Factor out parsing and allocation of IdentifierLoc objects.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@189833 91177308-0d34-0410-b5e6-96231b3b80d8
Update GCC attribute argument parsing comment to better reflect what's going on
here.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@189838 91177308-0d34-0410-b5e6-96231b3b80d8