Summary:
After applying replacements, redundant code like extra commas or empty namespaces
might be introduced. Fixer can detect and remove any redundant code introduced by replacements.
The current implementation only handles redundant commas.

Reviewers: djasper, klimek

Subscribers: ioeric, mprobst, klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D18551

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267416 91177308-0d34-0410-b5e6-96231b3b80d8