fix bug in file modes when mailing to files that didn't exist before;

fix bug in file modes when mailing to files that didn't exist before;
add an 'F' line to the .cf file that will read class entries from
another file, given a scanf string to do the parsing.

SCCS-vsn: usr.sbin/sendmail/src/deliver.c 3.43
SCCS-vsn: usr.sbin/sendmail/src/version.c 3.38
SCCS-vsn: usr.sbin/sendmail/src/readcf.c 3.14