Since the patch missed release 15.x and will be included in release 16.x. Also, simplify related tests.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D132414
DR692 handles two cases: pack expansion (for class/var template) and function parameter pack. The former needs DR1432 as a fix, and the latter needs DR1395 as a fix. However, DR1432 has not yet made a wording change. so I made a tentative fix for DR1432 with the same spirit as DR1395.
Reviewed By: aaron.ballman, erichkeane, #clang-language-wg
Differential Revision: https://reviews.llvm.org/D128745