updated to -mdoc version 3

updated to -mdoc version 3

SCCS-vsn: old/refer/addbib/addbib.1 6.4
SCCS-vsn: usr.bin/apply/apply.1 6.4
SCCS-vsn: usr.bin/apropos/apropos.1 6.10
SCCS-vsn: usr.bin/at/at/at.1 6.5
SCCS-vsn: bin/cat/cat.1 6.14
SCCS-vsn: usr.bin/at/atq/atq.1 6.5
SCCS-vsn: usr.bin/at/atrm/atrm.1 6.5
SCCS-vsn: usr.bin/basename/basename.1 6.6
SCCS-vsn: usr.bin/biff/biff.1 6.5
SCCS-vsn: usr.bin/cal/cal.1 6.8
SCCS-vsn: usr.bin/calendar/calendar.1 6.11
SCCS-vsn: usr.bin/checknr/checknr.1 6.6
SCCS-vsn: usr.sbin/chown/chgrp.1 6.6
SCCS-vsn: usr.bin/chpass/chpass.1 5.11
SCCS-vsn: usr.bin/cmp/cmp.1 6.5
SCCS-vsn: usr.bin/col/col.1 6.7
SCCS-vsn: usr.bin/colcrt/colcrt.1 6.7
SCCS-vsn: usr.bin/colrm/colrm.1 6.6
SCCS-vsn: usr.bin/column/column.1 5.8
SCCS-vsn: usr.bin/comm/comm.1 6.5
SCCS-vsn: usr.bin/compress/compress.1 6.9
SCCS-vsn: bin/cp/cp.1 6.12
SCCS-vsn: old/cpio/cpio.1 5.6
SCCS-vsn: bin/csh/csh.1 6.16