MFC r275366:

Pull in r209785 from upstream libc++ trunk (by Marshall Clow):

Fix a problem exposed by r208825, which caused bind (and other bits of
libc++) to stop working. And tests

This fix is needed to support clang 3.5.0 and higher, which are more
strict about forming pointer-to-function types with cv-qualifiers or
ref-qualifiers. See also the upstream PR http://llvm.org/PR19742 and
http://llvm.org/viewvc/llvm-project?rev=208825&view=rev

Reported by: amdmi3