Merge from PCH dev branch: patch for clang.


git-svn-id: https://root.cern.ch/svn/root/trunk@48977 27541ba8-7e3a-0410-8455-c3a389f83636
Should be relative to llvm/src/


git-svn-id: https://root.cern.ch/svn/root/trunk@48978 27541ba8-7e3a-0410-8455-c3a389f83636
Process the trailing nested transaction of decls that were collected during the commit of the current transaction even if there are no callbacks.
Move CodeGenModule::Reset() to where the initializers are run to enforce the survival of the global inits until they are run.


git-svn-id: https://root.cern.ch/svn/root/trunk@48979 27541ba8-7e3a-0410-8455-c3a389f83636
Simplify.


git-svn-id: https://root.cern.ch/svn/root/trunk@48985 27541ba8-7e3a-0410-8455-c3a389f83636