Given that the stated purpose of `CheckFailed()` is to provide a nice
spot for a breakpoint, it'd be nice not to have to use a regex to break
on it. Recover the ability to simply use `b CheckFailed` by
specializing the message-only version, and by changing the variadic
version to call into the message-only version.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232268 91177308-0d34-0410-b5e6-96231b3b80d8