Speculatively revert r354051 "Recommit Optional specialization for trivially copyable types"

and
r354055 "Optional specialization for trivially copyable types, part2"

These are suspected to cause Clang to get miscompiled on Ubuntu 14.04
(Trusty) which uses GCC 4.8.4. Reverting for an hour to see if this
helps. See llvm-commits thread.

> Recommit Optional specialization for trivially copyable types
>
> Unfortunately the original code gets misscompiled by GCC (at least 8.1),
> this is a tentative workaround using std::memcpy instead of inplace new
> for trivially copyable types. I'll revert if it breaks.
>
> Original revision: https://reviews.llvm.org/D57097

llvm-svn: 354126