Fixing a conflict detection bug in tooling::deduplicate

If a Replacment is contained within the conflict range being built, the
conflict range would be erroneously shortened. Now fixed. Tests updated to
catch this case.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188287 91177308-0d34-0410-b5e6-96231b3b80d8