might not be handled by the same FS as the directory (e.g. special device
files)...so it must be special-cased. This bug is seen when doing
"ln /dev/console /dev/foo" or equivilent and first appeared after I fixed
the argument order of VOP_LINK. YUCK! There really needs to be a way of
specifying what vp to use in the VCALL; doing this could fix the strategy
and bwrite special-cases, too.
