merge in tahoe support

merge in tahoe support

SCCS-vsn: sys/kern/init_main.c 7.2
SCCS-vsn: sys/kern/kern_clock.c 7.2
SCCS-vsn: sys/kern/kern_exec.c 7.2
SCCS-vsn: sys/kern/kern_exit.c 7.2
SCCS-vsn: sys/kern/kern_fork.c 7.2
SCCS-vsn: sys/kern/kern_sig.c 7.2
SCCS-vsn: sys/kern/kern_synch.c 7.2
SCCS-vsn: sys/kern/kern_time.c 7.3
SCCS-vsn: sys/kern/subr_prof.c 7.2
SCCS-vsn: sys/kern/subr_prf.c 7.3
SCCS-vsn: sys/kern/subr_xxx.c 7.2
SCCS-vsn: sys/kern/sys_process.c 7.2
SCCS-vsn: sys/kern/tty.c 7.3
SCCS-vsn: sys/kern/tty_subr.c 7.2
SCCS-vsn: sys/kern/tty_tb.c 7.2
SCCS-vsn: sys/ufs/ffs/ffs_subr.c 7.2
SCCS-vsn: sys/kern/kern_physio.c 7.2