smatch unreachable code checking needs reworking
The reasons are lost in the fogs of time (that is, last year), but for some reason, we have an
explicit list of no_return functions in smatch_data/. A quick test seems to indicate that it's at
least partly not necessary, because smatch does understand noreturn attribute.
Furthermore, we have "unreachable" globally disabled right now. I just ran smatch against
usr/src/lib and only got a few complaints. If we can, we should re-enable this check except
where we explicitly need to disable it.