value < 0.  errno is only updated in this case.  Change all (most?)
callers of syscalls to follow this better, and let's see if this strictness
helps us in the future.

ok deraadt@

Not sure what's more surprising: how long it took for NetBSD to
catch up to the rest of the BSDs (including UCB), or the amount of
code that NetBSD has claimed for itself without attributing to the
actual authors.
OK deraadt@

actually help us find bugs later (with lint, not cc), if they get
introduced

okay deraadt@, millert@, krw@

some brave soul should look at it.

opendev.h: ok, so I merged it with util.h
opendev.h: use util.h
everything else: use "util.h"

Add cpio.h, tar.h, and re_comp.h headers for POSIX & XPG4 conformance