Insert explicit casts to try appease overload resolution in the buildbots

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182514 91177308-0d34-0410-b5e6-96231b3b80d8
Comment and cleanup.

rdar://problem/13359718

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182524 91177308-0d34-0410-b5e6-96231b3b80d8