[clang-rename] Rename alias.

Summary:
* Support rename alias.
* Add unittests for renaming alias.
* Don't generate fixes for the SourceLocations that are invalid or in temporary
  buffer, otherwise crash would be happened when generating AtomicChanges.

Reviewers: ioeric

Reviewed By: ioeric

Subscribers: klimek, mgorny, cfe-commits

Differential Revision: https://reviews.llvm.org/D39043

llvm-svn: 316074