[ObjC] Make C++ triviality type traits available to non-trivial C

structs.

r326307 and r327870 made changes that allowed using non-trivial C
structs with fields qualified with __strong or __weak. This commit makes
the following C++ triviality type traits available to non-trivial C
structs:

__has_trivial_assign
__has_trivial_move_assign
__has_trivial_copy
__has_trivial_move_constructor
__has_trivial_constructor
__has_trivial_destructor

This reapplies r328680. This commit fixes a bug where the copy/move
__has_trivial_* traits would return false when a volatile type was being
passed. Thanks to Richard Smith for pointing out the mistake.

rdar://problem/33599681

Differential Revision: https://reviews.llvm.org/D44913

llvm-svn: 329289