Implement an "argparse" unique description of man pages and usage for root commands. 

Update 6.16 Release notes for TMVA (including updated form Kim) and update also  list of contributors

The previous version of the code in rooteventselector first applied
the cut by invoking CopyTree on the input TTree, getting an output
tree as a result. After that, it deactivated the branches to exclude
and called CloneTree on the aforementioned output tree, thus getting
the final tree. When following this strategy, the final tree is
bigger than the input tree, probably because the intermediate tree
data (before the cloning) is also stored.

In order to successfully combine the exclusion of branches and a cut
we need to reverse the order of operations: first deactivate branches
and clone the tree, then apply the cut with CopyTree.

Note that keeping the initial solution, only changing the call
to Write on the final tree with Write("", ROOT.TObject.kOverwrite)
does not work either.

Users might want to connect to a notebook server launched with
'root --notebook' from another computer. This setting of the
Jupyter configuration makes that possible.

This also solves the issue explained here:

https://github.com/ipython/ipython/issues/6193

Depending on the network configuration of a machine/container,
binding on localhost might fail. This looks like the issue
reported on ROOT-9829.

This makes the option() command honor normal variable
values when they are set.

This selects "GLVND" as default for OpenGL libraries
in the module to find OpenGL. The OLD behavior uses
the legacy library.

On Windows, these are e.g. 3.5 and 3.5.5, so comparing for
equality is too strict.

This is a very common problem that keeps hitting users and our own
builds in Jenkins. Failing to configure with an error message is the
best we can do to avoid runtime problems due to mismatched versions
of the Python interpreter and libraries.

- GetBranchNames is now a public method of RLoopManager
- fBranchNames is now RLoopManager::fValidBranchNames
- the first call to GetBranchNames evaluates the list of
  valid branch names (expensive operation) and stores it
  in fValidBranchNames. Subsequent calls simply return
  the cached value
- code in RInterface has been simplified as a consequence

the fix consists in a rewrite of the parser of enum fwd declarations which come
from dictionaries. Those are created by Cling's forward declarator.
The previous implementation was assuming namespace declarations and enum fwd
declarations on different lines, e.g.

namespace mystuff{
enum  __attribute__((annotate("$clingAutoload$myenum.h"))) myenum : unsigned int;
}

while in reality the declaration looks like
namespace mystuff{enum  __attribute__((annotate("$clingAutoload$myenum.h"))) myenum : unsigned int;}

Co-Authored-By: vgvassilev <v.g.vassilev@gmail.com>

* List all headers and sources
* Restrict includes to target
* Avoid shadow and extra warnings from OpenCascade

Right now, using the option -Dcompression_default=LZ4
configures ROOT with ZLIB and only emits a status message,
which is less visible than a CMake warning. Therefore,
make the option case-insensitive as well to accept ZLIB,
LZ4, and LZMA as recognized values.