[DGD] function pointers

[Shentino]

I must confess to being woefully inexperienced in closures.

The only exposure I had with them was on simud running on ldmud.

Their inability to be saved with save_object() proved to be a minor
irritation and was related to one of the more frequently reported bugs there
with peasants/peons getting disconnected from their ai modules.  They were,
however, useful as a shortcut.

Hopefully when/if closures bloom in dgd, a way to make them compatible with
online recompilation will be found.  I've got a few ideas on the subject but
there are some difficulties.

Interaction with recompilation was another major aspect of the discussion.
 Theoretical musings made it a very messy thing.