Make this portable to other OSs

Use NULL instead of 0.

pretty-print link addresses.

Use output buffer size to limit copy-out of sun_path. Otherwise you may
get a buffer overflow with strlcpy :)

Add a debugging format that prints all the fields with names.

branches: 1.9.4; 1.9.8; 1.9.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.8.10; 1.8.12;
In sockaddr_snprintf(sbuf, len, fmt, sa), do not write the terminating
null character outside of the byte region [sbuf, sbuf + len).

1) If the length of the buffer is 0, do not write a null character
at all. Previously, sockaddr_snprintf() may have been able to
overwrite sbuf[-1] if len was 0.

2) If the length of the buffer, len, is greater than 0, then write
the null at sbuf[len - 1]. Previously, sockaddr_snprintf()
wrote the null at buf[len - 1], where `buf' was a "cursor" that
did not necessarily equal `sbuf', the start of the buffer. Now,
sockaddr_snprintf() always writes the null at sbuf[len - 1].

Render the format %% as %.

branches: 1.6.4; 1.6.6;
Lint warnings.

Add the 'A' and 'P' format specifiers which use getaddrinfo(3) to turn
numbers into names (if possible). Also add the '?' format modifier
that elides the "N/A" if that's what you would normally get.

For consistency of sockaddr_snprintf(3) with snprintf(3) and
snprintb(3), do not count the terminating NUL in the return value.
Update the regression tests to match. Approved by christos@.

WARNS=3; fix cast-qual issues.

check for getnameinfo error correctly; thanks to Peter Postma.

Add sockaddr_snprintf; XXX: Needs a man page.