Revert "Small refactor on VectorizerHint for deduplication"

This reverts commit r215994 because MSVC 2012 can't cope with its C++11 goodness.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215999 91177308-0d34-0410-b5e6-96231b3b80d8