[Clang-tidy] Fix for crash in modernize-raw-string-literal check

Summary:
Clang-tidy modernize-raw-string-literal check crashes on run-time assert while it is evaluating compiler predefined identifiers such as
- __FUNCTION__
- __func__
- __PRETTY_FUNCTION__

Check is asserting because it cannot find opening quote for such string literal. It occurs only on debug build config.
I think that it would be good to prune such cases by crossing off predefined expressions - there is no need to evaluate such matches.

Reviewers: LegalizeAdulthood, alexfh

Subscribers: cfe-commits

Patch by Marek Jenda!

Differential Revision: http://reviews.llvm.org/D19331

llvm-svn: 266992