[Sema] Implement Core 2094: Trivial copy/move constructor for class with volatile member

Summary: This patch implements http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2094 which reverts Core 496.

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D32984

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302593 91177308-0d34-0410-b5e6-96231b3b80d8