C++ PATCHes to add __is_trivially_*

[Ville Voutilainen]

>>Ville asked for help with the necessary compiler intrinsics for the is_trivially_* >>C++11 library traits. The first patch cleans up a few oddities I noticed with the
>Great. I think this can be as well marked as PR c++/26099.

There's also PR c++/63362.

The intrinsics still fail to support certain variadic cases, such as

template <class T, class... Args> void bar() {
  static_assert(__is_trivially_constructible(T, Args...), "");
}