Refactor the Get* functions to be more consistant among themselves.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178613 91177308-0d34-0410-b5e6-96231b3b80d8
Use getPredefinesFileID() appropriately.

Thanks to Argyrios for the pointer.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178616 91177308-0d34-0410-b5e6-96231b3b80d8