new options to "window": shell, pty, frame

new options to "window": shell, pty, frame
and stuff to support them

SCCS-vsn: usr.bin/window/main.c 3.23
SCCS-vsn: usr.bin/window/wwopen.c 3.16
SCCS-vsn: usr.bin/window/ww.h 3.29
SCCS-vsn: usr.bin/window/cmd.c 3.29
SCCS-vsn: usr.bin/window/cmd1.c 3.25
SCCS-vsn: usr.bin/window/wwgets.c 3.6
SCCS-vsn: usr.bin/window/cmd2.c 3.29
SCCS-vsn: usr.bin/window/defs.h 3.14
SCCS-vsn: usr.bin/window/wwclose.c 3.10
SCCS-vsn: usr.bin/window/error.c 3.9
SCCS-vsn: usr.bin/window/:ww 1.9
SCCS-vsn: usr.bin/window/cmd6.c 3.11
SCCS-vsn: usr.bin/window/lcmd.c 3.18
SCCS-vsn: usr.bin/window/lcmd1.c 3.22
SCCS-vsn: usr.bin/window/wwenviron.c 3.10
SCCS-vsn: usr.bin/window/wwspawn.c 3.8
SCCS-vsn: usr.bin/window/wwiomux.c 3.10
SCCS-vsn: usr.bin/window/win.c 3.8
SCCS-vsn: usr.bin/window/lcmd2.c 3.3