Fix some cases where StringRef was being passed by const reference. Remove const from some other StringRefs since its implicitly const already.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216820 91177308-0d34-0410-b5e6-96231b3b80d8
Add a test for converting ArrayRef<T *> to ArrayRef<const T *>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216821 91177308-0d34-0410-b5e6-96231b3b80d8
Use StringRef to avoid copies and simplify code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216822 91177308-0d34-0410-b5e6-96231b3b80d8
Remove 'virtual' keyword from methods markedwith 'override' keyword.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216823 91177308-0d34-0410-b5e6-96231b3b80d8