Fix for PR17606 - result_of (and INVOKE) works incorrectly for member function pointers with ref qualifiers. Also a drive-by fix for common_type in C++03 mode. Thanks to Michel Morin for the bug report and the proposed fix.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@201101 91177308-0d34-0410-b5e6-96231b3b80d8