man/man3/*printf.3: Document ERRORS

man/man3/*printf.3: Document ERRORS

The printf family of functions set errno if a negative value is returned.

Source is POSIX.1, see
<https://pubs.opengroup.org/onlinepubs/9799919799/functions/fprintf.html>
<https://pubs.opengroup.org/onlinepubs/9799919799/functions/fwprintf.html>

Also see manual pages of FreeBSD and OpenBSD.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Message-ID: <34octlcodbwm3kfqlouvrvhriiftmlzzobbohgzivlkgi53nfs@7gxajeb56klz>
Signed-off-by: Alejandro Colomar <alx@kernel.org>