[PATCH] [libcxx] Remove use of default function template parameters in type traits. Fixes DR20484

[Dan Albert]

Well, I still can't get a passing checkbuild (though I can build a system image) with ToT libc++, but it's a different set of issues now (partially due to bugs in our version of gcc). I think this patch is good to go.

http://reviews.llvm.org/D4735