Revert "[libc++] Correctly handle Objective-C++ ARC qualifiers in std::is_pointer"

This broke the Chromium build on Mac, see https://crbug.com/949071

> Summary:
> Otherwise, std::is_pointer<id __strong> works, but std::is_pointer<id __weak>
> (and others) don't work as expected.
>
> rdar://problem/49126333
>
> Reviewers: ahatanak, EricWF
>
> Subscribers: christof, jkorous, dexonsmith, libcxx-commits
>
> Differential Revision: https://reviews.llvm.org/D60087

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@357569 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed