re-roll-forward "[clang] Mark `trivial_abi` types as "trivially relocatable"".""

This reverts commit b0bc93da.

Changes: `s/_WIN32/_WIN64/g` in clang/test/SemaCXX/attr-trivial-abi.cpp.

The calling convention is specific to 64-bit windows. It's even in the name: `CCK_MicrosoftWin64`.

After this, the test passes with both `-triple i686-pc-win32` and `-triple x86_64-pc-win32`. Phew!

Reviewed By: gribozavr2

Differential Revision: https://reviews.llvm.org/D123059