Add a subgroup of c++1z-compat to enable and disable the warning about
c++17's non-throwing exception specification in function signature.

rdar://problem/32628743

Differential Revision: https://reviews.llvm.org/D34251

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@305772 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 1411862c164184d226cfd802ea1c60d4f2500337)
3 files changed