Bonuses work again

[Eero Tamminen]

Hi,

I've commited updated support for bonuses to the CVS.
All the four sprite types involved are in sprites/bonusmachine.c.
All bonus parsing and handling is in engine/bonus.c.

Playing the game for a while will eventually get an error about killing an
unregistered object, which I haven't yet tracked down.  Anyway, you can test
this with levels 3&4 which have now bonuses (one of the them is the amazing
bouncing hippo ;-)).

Additionally I moved "sprite" parsing from level.c to sprite_types.c
that way sprite_types dict can be static.


	- Eero

Btw. I updated last thursday birds to new refcounting mechanism, so
they once again follow each other (in case somebody had time to miss
this)...