Darwin: remove buggy assertion

We later emit a proper error in the situations where this would trigger, so
there's no need to check.

rdar://problem/16040604

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201508 91177308-0d34-0410-b5e6-96231b3b80d8
Fix gcc warning about C++ style comments.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201512 91177308-0d34-0410-b5e6-96231b3b80d8