This reverts commit 6fa43c88.

as suggested on the ROOT forum (https://root-forum.cern.ch/t/please-correct-bug-reading-date-time-from-postgresql-tpgsqlstatement)

[net/monalisa/src/TMonaLisaWriter.cxx:956] -> [net/monalisa/src/TMonaLisaWriter.cxx:957]: (error) Iterator 'iter' used after element has been erased.
[proof/proofd/src/XrdProofdProofServMgr.cxx:4648] -> [proof/proofd/src/XrdProofdProofServMgr.cxx:4646]: (error) Iterator 'iter' used after element has been erased.

[math/minuit2/src/Minuit2Minimizer.cxx:669] -> [math/minuit2/src/Minuit2Minimizer.cxx:669]: (style) Same expression on both sides of '||'.
[math/minuit2/src/Minuit2Minimizer.cxx:736] -> [math/minuit2/src/Minuit2Minimizer.cxx:736]: (style) Same expression on both sides of '||'.
[math/minuit2/src/Minuit2Minimizer.cxx:753] -> [math/minuit2/src/Minuit2Minimizer.cxx:753]: (style) Same expression on both sides of '||'.

[tree/tree/src/TBasket.cxx:852]: (style) Redundant condition: If 'flag >= 80', the comparison 'flag' is always true.
[misc/table/src/TFileIter.cxx:467] -> [misc/table/src/TFileIter.cxx:468]: (warning) Identical condition 'thisRunNumber<runNumber', second condition is always false

[math/mathcore/src/TMath.cxx:826]: (style) Array index 'ia' is used before limits check.
[math/mathcore/src/TMath.cxx:830]: (style) Array index 'ib' is used before limits check.
[math/mathcore/src/triangle.c:15434]: (style) Array index 'aspectindex' is used before limits check.
[roofit/roofit/src/RooIntegralMorph.cxx:375]: (style) Array index 'igapHigh' is used before limits check.

[core/winnt/src/TWinNTSystem.cxx:5035]: (style) Statements following return, break, continue, goto or throw will never be executed.
[tree/treeplayer/src/TSelectorDraw.cxx:380]: (style) Statements following return, break, continue, goto or throw will never be executed.

[net/auth/src/TAuthenticate.cxx:4205]: (error) Resource leak: fd
[roofit/roofitcore/src/BidirMMapPipe.cxx:1880]: (error) Memory leak: s
[tree/tree/src/TLeaf.cxx:222]: (error) Memory leak: countname
[tree/tree/src/TLeaf.cxx:226]: (error) Memory leak: countname
[tmva/tmva/src/MethodBase.cxx:2783]: (error) Memory leak: pdfS
[tmva/tmva/src/MethodBase.cxx:2783]: (error) Memory leak: pdfB

[roofit/roofitcore/src/RooAbsArg.cxx:280]: (style) Redundant checking of STL container element existence before removing it.

[core/dictgen/src/rootcling_impl.cxx:457]: (performance) Possible inefficient checking for 'fieldSelRules' emptiness.
[core/dictgen/src/rootcling_impl.cxx:4573]: (performance) Possible inefficient checking for 'filesIncludedByLinkdef' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:322]: (performance) Possible inefficient checking for 'fWebConn' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:374]: (performance) Possible inefficient checking for 'fCmds' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:419]: (performance) Possible inefficient checking for 'fWebConn' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:475]: (performance) Possible inefficient checking for 'fWebConn' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:587]: (performance) Possible inefficient checking for 'fCmds' emptiness.
[gui/canvaspainter/v7/src/TCanvasPainter.cxx:787]: (performance) Possible inefficient checking for 'fCmds' emptiness.
[html/src/TDocParser.cxx:684]: (performance) Possible inefficient checking for 'currentType' emptiness.
[proof/proofd/src/XrdProofdManager.cxx:804]: (performance) Possible inefficient checking for 'uwrks' emptiness.
[proof/proofd/src/XrdProofdSandbox.cxx:467]: (performance) Possible inefficient checking for 'staglst' emptiness.
[proof/proofd/src/XrdProofdSandbox.cxx:571]: (performance) Possible inefficient checking for 'actln' emptiness.
[roofit/roofitcore/src/RooSimWSTool.cxx:574]: (performance) Possible inefficient checking for 'slist' emptiness.

all the reports Prefer prefix ++/-- operators for non-primitive types

This breaks the classic build with --enable-pgsql since the internal
header may not be found in the expected place for PostgreSQL 10.x.

This breaks the build with -Dmysql=ON since the internal header will
not be found.

this affects the order in which the libraries are loaded and ultimately
the order in which the streamer infos are present on the files.
This affects the roottest-root-io-filemerger-make test, very sensitive
to the file size on disk which in turn is sensitive to the size (and compression factor)
of the TStreamerInfo record.

This refactors the CMake build files to no longer manually call
the CMake functions for generating and linking the dicionairies.
One reason is to reduce boilerplate, the other is that it is now
no longer possible to have naming mismatches between the dictionary
generation arguments and linking function arguments which was causing
the race conditions we had in our build system.

This also now follows more strictly the separation between dependencies
like Math, Tree and Core and pure linking flags to external libraries.

If the G__X filenames don't match with a module called X, then
CMake can't find the right dependencies and we get race conditions.
This patch fixes all a few more typos that caused those problems.

The naming of the library in the two function calls ROOT_GENERATE_DICTIONARY
and ROOT_LINKER_LIBRARY was often not matching. This causes that
ROOT_LINKER_LIBRARY couldn't correctly set its dependencies to the output
file of ROOT_GENERATE_DICTIONARY and therefore causes race conditions in
the build system.

Note: We're attached all dependencies to a custom target, and
NOT to the output files generated by rootcling. This should mitigate
the race conditions we experience when multiple targets in different
Make jobs request the same output file as a dependency and then
suffer from this Make problem that is described here:
https://cmake.org/Bug/view.php?id=10082

This patch also adds a (commented out) piece of code that can print
warnings if we don't have a fitting G__*.cxx file for a
ROOT_LINKER_LIBRARY call. This is sometimes intended, so I didn't
enable this warning by default. We should enable this code
by default in the future once we have a way to express if we
intentionally don't provide the G__*.cxx file when calling
ROOT_LINKER_LIBRARY.

ROOT_GENERATE_DICTIONARY allows to specify dependencies, but we currently
don't actually specify those. As we need this for getting the module
dependencies right (as we can't build missing modules on demand), we should
add those dependencies here. Then those dependencies propagate to the
rootcling invocation which will in the future also generate the C++ module
for the selected dictionary.

ClassImp is a macro defined in Rtypes.h. It can be written without trailing
semicolon. However, clang-format is based on lexing and it doesn't know at
all about preprocessors and how to expand macros. When visiting ClassImp(X)
it thinks this is not a completed entity (as it doesn't expand macros) and
considers the next line as continuation of the previous.

Inserting a semicolon fixes the issue and makes formatting with clang-format
in the ROOT codebase less tricky.

This patch improves the previous check whether the current compiler
is using an incompatible libstdc++ version or not.

Many headers contains redundant header guards around #include directives:

    #ifndef ROOT_TTree
    #include "TTree.h"
    #endif

This patch removes the #ifndef's around these includes as they
don't serve any pratical purpose anymore and are no longer part
of the current ROOT coding convention.

This patch also fixes the 153 typos that are contained in the
symbols of the #ifndef directives.

Signed-off-by: Vassil Vassilev <vvasilev@cern.ch>

Make cannot deal with 'export *', they have to be escaped and fixed later on.

This is the recommended way of using the modules feature and should pave our way
of enabling -fmodules-local-submodules-visibility mode.

Our two build systems can generate almost entirely a modulemap file laying out
one module per library. Due to some non-modular implementation in ROOT's core we
still need to treat some header files specially.

This patch appends modular header files to the modulemap while skipping the
predefined ones. Configure-make relates all headers that are installed in
$ROOTSYS/include to their library whereas relates only headers which are part of
library's dictionary.

See https://root.cern.ch/phpBB3/viewtopic.php?f=3&t=20835

Support for gcc 5.1. Define _GLIBCXX_USE_CXX11_ABI=0 for files using the Oracle occi binary library.

as it spoils cc7 compatibility.
Clean useless CINT include guards.

and an actual bug (a tautology in an if condition) in TH3

Fix Jira issue #ROOT-6511 TSQLiteStatement: Missing / wrong check for column index, failing IsNull(), as reported by Oliver Freyermuth:
Finally, my colleagues managed to uncover a small issue in my TSQLiteStatement implementation:
"IsNull()" checked the column-count in the wrong way (it used the number of bound columns which is only valid in prepared inserts).
I have done the following changes to TSQLiteStatement in the attached patch:
1. In fNumPars, I now store either the "bind" columns for a prepared statement with bound parameters, or the number of returned columns for a simple select without binding. This also simplifies error handling and TSQLiteStatement::GetNumFields() now just returns the variable which is correct in both working modes.
2. All Get'ters now check the column-number consistently, as the SQLite-documentation states that "get"ting an invalid column number returns undefined results. Note that for bound parameters, SQLite behaves differently and does the error handling itself (which I already check in TSQLiteStatement).