Explicitly annotate setjmp() and longjmp() (and friends) as __returns_twice and __dead instead of depending on GCC's special handling of these function names.
Explicitly annotate setjmp() and longjmp() (and friends) as
__returns_twice and __dead instead of depending on GCC's special
handling of these function names.

With input from kettenis@ and guenther@
Fixes a warning from clang
ok matthew@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars