Embedding and stack

Okay, here's the rules for PMCs that live outside parrot, and calling 
into parrot from the outside.

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
[email protected]                         have teddy bears and even
                                       teddy bears get drunk