mount_ifs: repocopy of sbin/mount, with most of the intelligence ripped out
and "ufs" replaced with "ifs" in the right places. It will only
mount a single filesystem, rather than the -t <type> magic that
our real mount does.
fsck_ifs: repocopy of sbin/fsck_ffs, but the directory structure stuff
(pass2 and some refcount checks) has been #ifdef'ed out.
src/sbin/Makefile: Build these two utilities
There is probably cruft code left in both which can be removed at a later
date, especially in mount_ifs, but I trust that people will not try
mount_ifs -a ..
Note: there are no man pages installed for these two commands as I haven't
actually written them yet.