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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@316074 91177308-0d34-0410-b5e6-96231b3b80d8