[OpenBIOS] Fixing interpose

[Blue Swirl]

Fixing the handling of interposed devices would allow booting a lot more OSes.

If I understand correctly the interpose solution discussed earlier,
the ihandle>phandle in line 28 in:
http://www.openbios.org/viewvc/openbios-devel/forth/device/package.fs?view=annotate&root=OpenBIOS
should become more like something in OBP line 72:
http://openbios.org/viewvc/obp/os/bootprom/instance.fth?view=annotate&root=OpenBOOT

Is this right? Or could someone more knowledgeable in Forth propose a fix?