New cover scheme

New cover scheme

SCCS-vsn: usr.bin/window/wwopen.c 3.13
SCCS-vsn: usr.bin/window/ww.h 3.19
SCCS-vsn: usr.bin/window/cmd.c 3.15
SCCS-vsn: usr.bin/window/wwclose.c 3.6
SCCS-vsn: usr.bin/window/wwframe.c 3.11
SCCS-vsn: usr.bin/window/wwlabel.c 3.8
SCCS-vsn: usr.bin/window/:ww 1.5
SCCS-vsn: usr.bin/window/cmd6.c 3.3
SCCS-vsn: usr.bin/window/wwadd.c 3.6
SCCS-vsn: usr.bin/window/wwdelete.c 3.6
SCCS-vsn: usr.bin/window/wwdump.c 3.9
SCCS-vsn: usr.bin/window/wwinschar.c 3.10
SCCS-vsn: usr.bin/window/wwunframe.c 3.9
SCCS-vsn: usr.bin/window/wwdelchar.c 3.7
SCCS-vsn: usr.bin/window/wwcursor.c 3.4
SCCS-vsn: usr.bin/window/wwmove.c 3.4