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 :-)
a string containign 'J'.
o Properly terminate argv list with a NULL entry.
o Use warn() to report the exec failure because free could change errno and
err would report the wrong reason.
o Don't terminate string to err with ':' since this results in two colons.
