Follow-up PR #376 from M Ellert

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>

This reverts commit 83e4099f.

This reverts commit 5c076c6c.

This reverts commit 92c7310f.

This reverts commit b406328d, reversing
changes made to 318c7a47.

Replaces if(builtin_foo) statements with explicit support in the
various ROOT macros.

This removes ROOT_ADD_BUILTIN_DEPENDENCIES and adds BUILD_BYPRODUCTS
for the external projects.  This way, the build system can explicitly
depend on the output file of the external project instead of introducing
a hidden dependency..

If necessary it still could be accessed through TAuthenticate.

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.

This remove duplicate definitions and duplicate default argument errors when
building modules for proof.

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.

rpdp headers are not part of the ROOT public API and thus should not
be visible in include/. They were simply because multiple ROOT modules
were including them, and we had no way to specify that other than
publishing them. Now we have a new directory next to src/ and inc/:
res/ (as in "reserved" or "restricted"), signalling that these headers
are not public but used by other ROOT modules.

Update the Moduke.mk-s accordingly.

Move a few really private headers into their src/ directories.

Signed-off-by: Philippe Canal <pcanal@fnal.gov>

Signed-off-by: Sergey Linev <S.Linev@gsi.de>
Signed-off-by: Philippe Canal <pcanal@fnal.gov>

A fix is also available upstream in civetweb soon, see:
https://github.com/civetweb/civetweb/issues/349