MFC r318257,r318278:

MFC r318257,r318278:

r318257:

style(9): sort headers

r318278:

Mark errf _Noreturn, and mark errf and warn __printflike

The _Noreturn attribute was added to placate Coverity and other static
analysis tools. The __printflike attribute was added to catch issues
with the calls related to printf(3) abuse.

- Modify the code to facilitate the __printflike attribute addition.
- Convert errf calls in to_mb(..) and to_mb_string(..) to warn(..) so
  the calls will return instead of exiting, as the code suggests it
  should.