[PATCH] [libc++] Teach is_integral, is_[un]signed and make_[un]signed about __[u]int128_t

[Marshall Clow]

  The HugeEnum test fails when compiled with -std=c++03.

  It needs to be wrapped in a "#if _LIBCPP_STD_VER > 11" block (see test/utilities/function.objects/unord.hash/enum.pass.cpp for an example)

http://llvm-reviews.chandlerc.com/D2917