Add semantic checking for template arguments that correspond to

non-type template parameters that are references to functions or
pointers to member functions. Did a little bit of refactoring so that
these two cases, along with the handling of non-type template
parameters that are pointers to functions, are handled by the same
path. 

Also, tweaked FixOverloadedFunctionReference to cope with member
function pointers. This is a necessary step for getting all of the fun
member pointer conversions working outside of template arguments, too.

llvm-svn: 64277