Debug Info: remove use of magic numbers to tweak specific debug info metadata fields

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178079 91177308-0d34-0410-b5e6-96231b3b80d8
<rdar://problem/13473493> Handle 'this->' insertion recovery within trailing return types.




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178081 91177308-0d34-0410-b5e6-96231b3b80d8