[libclang] Introduce clang_Type_getCXXRefQualifier whichexposes ref-qualifier information of function type.

Patch by Che-Liang Chiou!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192493 91177308-0d34-0410-b5e6-96231b3b80d8