close cached MCI connections after a fork; add p (privacy) and b

close cached MCI connections after a fork; add p (privacy) and b
(min blocks free) options; fix selfref code; clean up $#error format

SCCS-vsn: usr.sbin/sendmail/src/headers.c 6.8
SCCS-vsn: usr.sbin/sendmail/src/pathnames.h 6.2
SCCS-vsn: usr.sbin/sendmail/src/recipient.c 6.13
SCCS-vsn: usr.sbin/sendmail/src/main.c 6.21
SCCS-vsn: usr.sbin/sendmail/src/envelope.c 6.10
SCCS-vsn: usr.sbin/sendmail/src/parseaddr.c 6.17
SCCS-vsn: usr.sbin/sendmail/src/domain.c 6.6
SCCS-vsn: usr.sbin/sendmail/src/collect.c 6.5
SCCS-vsn: usr.sbin/sendmail/src/sendmail.h 6.14
SCCS-vsn: usr.sbin/sendmail/src/savemail.c 6.7
SCCS-vsn: usr.sbin/sendmail/src/srvrsmtp.c 6.11
SCCS-vsn: usr.sbin/sendmail/src/readcf.c 6.9
SCCS-vsn: usr.sbin/sendmail/src/deliver.c 6.19
SCCS-vsn: usr.sbin/sendmail/src/queue.c 6.14
SCCS-vsn: usr.sbin/sendmail/src/conf.c 6.18
SCCS-vsn: usr.sbin/sendmail/src/alias.c 6.14
SCCS-vsn: usr.sbin/sendmail/src/udb.c 6.9
SCCS-vsn: usr.sbin/sendmail/src/mci.c 6.4