Fix a crash in cppcoreguidelines-pro-type-member-init when checking a class...

Fix a crash in cppcoreguidelines-pro-type-member-init when checking a class that initializes itself as a base

Summary: Fix a crash when a record type initializes itself in its own base class initializer list.

Patch by Michael Miller!

Reviewers: alexfh, aaron.ballman, hokein

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D19802

llvm-svn: 268369