This addresses ROOT-6130

The implementations relies on these points:
 o The fieldDecl is decorated with an attribute carrying the information
   about iotype and ioname.
 o The TClingDataMemberInfo overrides the TypeName and Name with the
   values of the iotype and ioname if specified.

In addition, rootcling refuses (with a nice message) to assign an iotype
in case genreflex is used and the actual data member to be changed is a pod.

Add an optimised way to access properties' names and values has been added
to make the operations in TClingDataMemberInfo as fast as possible.

Remove unused variables.

- The toolbar methods now work without XOR mode (useful for OpenGL()).

Implement Set[X-Y][1-2]() for TPave and inherited classes to make sure the NDC coordinates are also defined.

Thanks to Lorenzo.

it's a batch.

machine without a login session.

__cxa_atexit is generated by clang::CodeGen upon seeing the first static
destructor. Instead of trying to provoke that we just continue to search for it.

Remove trigger__cxa_atexit(), we will just remap until successful.
Remove unused dso parameter.
Instead of friending just provide a function.
Pass a transaction, the typesafe way.

Relax tolerance for some tests on Apple platforms

skip c++11 compilation of tests for 10.8 clang 4  (3.3), which gives au undefined symbol in numeric_limits::digits