LLVM r236120 renamed debug info IR constructs to use a `DI` prefix, now
that the `DIDescriptor` hierarchy has been gone for about a week. This
commit was generated using the rename-md-di-nodes.sh upgrade script
attached to PR23080, followed by running clang-format-diff.py on the
`lib/` portion of the patch.
llvm-svn: 236121
Add a frontend test for PR22929, which was fixed by LLVM r232449.
Besides the crash test, check that the `!dbg` attachment is sane since
its presence was the trigger.
llvm-svn: 232450