Update add.to.pic to use the additional animated object slot

[lanceewing]

The original AGI interpreter allocated an additional animated object slot in its table of animated objects for the use of the "picobj", i.e. the add.to.pic. This is kind of a temporary animated object, as it ceases to be used after the add.to.pic is added to the picture, but it does appear to be saved to the save game files. So to more closely match what the original interpreter is doing, we should change AGILE to use an additional slot at the end of the GameState AnimatedObjects array for that purpose, rather than creating an AnimatedObject on the fly. We'll then get a saved game file one step closer to the original interpreter.

[lanceewing]

Closing, as it has been clarified that this is not how it works in the original AGI interpreter code.