Handle passing non-Qualtypes to %diff better.  Instead of asserting, fall back
to printing the default case.  This is a fix for PR15023.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173965 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "[preprocessor] Don't warn about "disabled expansion of recursive macro""

This reverts commit r173952

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173970 91177308-0d34-0410-b5e6-96231b3b80d8