Tooling: Ignore file names in tooling::deduplicate.

This was horribly broken due to how the sort predicate works. We would
report a conflict for files with a replacement in the same position but
different names if the length differed. Just ignore paths as this is often
what the user wants. Files can occur with different names (due to symlinks
or relative paths) and we don't ever want to do the same edit in one file
twice.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217439 91177308-0d34-0410-b5e6-96231b3b80d8