Fix ambiguity detection in GetBestOverloadCandidateSimple.

When performing the simplistic overload resolution for single-argument methods,
don't check the best overload for ambiguity with itself when the best overload
doesn't happen to be the first one.

Fixes PR13480.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160961 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed