Fix failing -verify tests due to change in Clangs static_assert message.

Clang recently changed the way it outputs static assert diagnostics.
This patch fixes libc++'s -verify tests so they tolerate both the old
and new message format.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@313499 91177308-0d34-0410-b5e6-96231b3b80d8
12 files changed