Introduce type constant and cast macro to obsolete DO_UPCAST().

Prepares for ISA realizefn.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Message-id: 1367093935-29091-14-git-send-email-afaerber@suse.de
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>