1) *ALL* PMCs which are created outside parrot must be registered
(unless they're otherwise anchored)
2) No call into parrot from the outside needs to pass in a stack top
(though it may via a separate call if it so chooses)
3) The embedding wrapper is responsible for setting and resetting the
top of stack.

While I don't want the extension interface to register PMCs by
default (since that's generally unneccesary) I'm OK beefing up the
interface to have an allocate-and-register version.
--
                                         Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
d...@sidhe.org                         have teddy bears and even
                                       teddy bears get drunk