Implement VOP_PARSEPATH() for hfs.

This checks for a following "/rsrc" at the end of the pathname (to
indicate the resource fork of a file) and assimilates it into the
component name to be looked up. Then cn_namelen will already include
this text in lookup, and it's no longer necessary to muck with
cn_consume.

Invalid uses of "/rsrc" are ignored rather than rejected, which
appears to be the same as the old behavior. It is possible that the
parsepath logic should only consume the "/rsrc" if the name names a
file and not a directory, which would require looking it up in
parsepath and be a general nuisance; I hope not. It's also possible
that the whole thing doesn't work at all now, or it didn't before, as
I don't have any way to test it.

(dholland)