fix HELO problem in srvrsmtp (HELO was required); fall back to

fix HELO problem in srvrsmtp (HELO was required); fall back to
other MX records if error occurs on MAIL or DATA; prototype portability;
change $~ to just match one word; fix some problems with multi-word matches

SCCS-vsn: usr.sbin/sendmail/src/version.c 6.46