major rework; fixup netstat stuff; pull disk cmds into common file; change

major rework; fixup netstat stuff; pull disk cmds into common file; change
everthing related to disks to use dk_ndrive and global selction; use getw where possible

SCCS-vsn: usr.bin/systat/Makefile 1.8
SCCS-vsn: usr.bin/systat/cmds.c 1.7
SCCS-vsn: usr.bin/systat/disks.c 1.3
SCCS-vsn: usr.bin/systat/fetch.c 1.5
SCCS-vsn: usr.bin/systat/iostat.c 1.8
SCCS-vsn: usr.bin/systat/keyboard.c 1.5
SCCS-vsn: usr.bin/systat/main.c 1.9
SCCS-vsn: usr.bin/systat/mbufs.c 1.6
SCCS-vsn: usr.bin/systat/netstat.c 1.2
SCCS-vsn: usr.bin/systat/pigs.c 1.8
SCCS-vsn: usr.bin/systat/swap.c 1.8
SCCS-vsn: usr.bin/systat/systat.h 1.6