When noting that a TStreamerInfo set has already been processed, we
must do it in 3 separates steps:
  - check it was seen before
  - read and process the set
  - record that the set as been seen.

The previous situation:
  - check and record that the set as been seen
  - read and process the set
led to a race condition if a second thread was checking the same
set before the second step was completed (in which case the
second thread was believing that the set was process and looking
for the result of the process (one of the StreamerInfo) but could
not find it.

We extend RConcurrentHashColl to have 2 new operations
  - standalone Hash calculation
  - standalone Find of hash
  - standalone Insert of hash.
and we use it to split the check and the recording as described
previously.

(this is an addendum to 95bf468438)

The INCLUDE_DIRECTORIES property only became available in
CMake 3.11, so we have to use COMPILE_FLAGS instead, which
is already available in our required version (CMake 3.4.3).

This reverts commit 80b1a73b.

The patch triggers a pre-existing bug on fedora28 and gcc8.1

This is a better implementation over doing #ifdef R__USE__CXXMODULES
everywhere.

if the size is bigger than the default value. Document better the behaviour, too.

but rather for the missing dictionary of T given the way in which we
treat unique_ptrs.

Previously, [system] was used to mark modules which were supporsed be
implicitly built by rootcling for runtime modules. This was a workaround, and it was causing
SourceLocation error in cxxmodules as it is also using the same
modulemap.

To remove the workaround, we are introducing a new convention that modules
start with ROOT_ is treated as "ROOT system modules", which can be build
implicitly.

This was updated in commit fe4ffa75,
but that commit only changed this on UNIX and missed Windows.

Issue: ROOT-9532

(cherry picked from commit f4801313)

This reverts commit 316f5535.

TBB is not included as system anymore, so we need to avoid
warnings from its headers using a different method.

This causes problems both in depedency generation, since clang ignores
headers marked as system, and due to the order in which headers are
processed (build directory is marked as system when TBB is builtin).

when looking for enumerators.

This reverts commit dc825fc4.

* Centralise the generation of help for root command

Add argparse2help.py, add root-argparse.py, delete the old help of root, add the cmake commands needed to generate the header containing the command line options help and to generate manual page for the root command.

The python file argparse2help.py can be called with the root-argparse.py and the output name as arguments. This call will generate the header file if the output has an extension ".h" and will generate the manual page if the extension is ".1"

* Centralise the generation of help for the rest of the commands

Add cmake changes to generate headers and manual pages for rootcling hadd and hist2workspace
Delete old man pages of hadd and hist2workspace
Add commented out generation of man pages for python commands, we need to add a dependency before uncommenting them out
Add hadd rootcling hist2workspace argparse modules

* make the path compatible with windows

* review modifications

* add dependency on the input and the generation script of man pages

* remove installation of headers

* Update CMakeLists.txt

It makes no sense to generates man pages on Windows. Windows does not have the `man` command.

* Update argparse2help.py

* Update argparse2help.py

* Update argparse2help.py

* Update hadd.cxx

haddCommandLineOptionsHelp.h was not included for windows

* Update root-argparse.py

add the option --version

* Update argparse2help.py

simplified version (Thanks Bertrand !)

Added --version to TApplicattion

Included commit hash and architecture

removed mistake

ROOT-9620 #close

This reverts commit 5993be60, reversing
changes made to f6b75592.

* Revert "[cmake] Narrow the list of included directories."

This reverts commit 88c16588.

* Revert "[cxxmodules] Build cling runtime into module."

This reverts commit 76a9ce75.

This reverts commit 783cddc4.