Fixed a bug regarding result_of reported by Sven Behne. The fix is C++11 only...

Fixed a bug regarding result_of reported by Sven Behne.  The fix is C++11 only mainly because result_of is a variadic beast and working with variadics is just such a problem in C++03 mode.  This should bring result_of up to full conformance with the C++11 spec.

llvm-svn: 159211