Import revision 48376 from the v5-34-00 patch branch:
Extend STLArgs to properly support std::bitset.
This fixes <http://savannah.cern.ch/bugs/?99947>


git-svn-id: https://root.cern.ch/svn/root/trunk@48377 27541ba8-7e3a-0410-8455-c3a389f83636