Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Merge from OpenBSD:
o Realloc memory leak fixed which won't matter but would trigger purify
o Default to sendmail when no mailer.conf exists.

Fixed bugs in OpenBSD version:
o Add NULL termination in the right place.

Also put back the err. free shouldn't touch errno.

Pointed out by: theo de raadt (except the NULL bug :-)

Move mailer.conf to /etc/mail at obrien's request.

Make mailwrapper build