This lets you resolve pathnames to their underlying physical path:
critter# realpath /sys/kern/subr_disk.c
/freebsd/src/sys/kern/subr_disk.c
Update the pwd man-page slightly.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
