add POSIX/IEEE contribution notice

add POSIX/IEEE contribution notice

SCCS-vsn: usr.bin/basename/basename.1 6.7
SCCS-vsn: bin/cat/cat.1 6.16
SCCS-vsn: share/man/man1/cd.1 6.6
SCCS-vsn: usr.sbin/chown/chgrp.1 6.7
SCCS-vsn: bin/chmod/chmod.1 6.14
SCCS-vsn: usr.bin/cksum/cksum.1 5.5
SCCS-vsn: usr.bin/cmp/cmp.1 6.7
SCCS-vsn: usr.bin/comm/comm.1 6.7
SCCS-vsn: bin/cp/cp.1 6.14
SCCS-vsn: usr.bin/cut/cut.1 5.5
SCCS-vsn: bin/date/date.1 6.15
SCCS-vsn: bin/echo/echo.1 6.7
SCCS-vsn: usr.bin/printenv/printenv.1 6.6
SCCS-vsn: usr.bin/false/false.1 6.5
SCCS-vsn: usr.bin/find/find.1 6.26
SCCS-vsn: usr.bin/join/join.1 6.6
SCCS-vsn: bin/kill/kill.1 6.7
SCCS-vsn: bin/ln/ln.1 6.7
SCCS-vsn: bin/ls/ls.1 6.18
SCCS-vsn: bin/mkdir/mkdir.1 6.9
SCCS-vsn: usr.bin/mkfifo/mkfifo.1 5.5
SCCS-vsn: bin/mv/mv.1 6.8
SCCS-vsn: usr.bin/nohup/nohup.1 6.7