Cleaned up the Message System

[Sophia]

The message system, as originally conceived, was actually something of a different design than what actually got implemented. To be honest, I'm not quite sure what I was trying to do-- I like the way it turned out, though. Anyway, I saw no use in keeping that strange gap between M_TOGGLE which uses msg id 2 and M_DESTROY at 255, and then putting a lot of extra messages above 255. There's also no reason, other than convention, to use such low numbers.

I've changed the base code around so that the base code uses message id's above 100000. That way designers can create whatever crazy message id they could think of (provided it's in the range 0-99999 anyway) and it won't clash with any present or future system messages.

Don't worry too much about compatibility, this change won't even be noticed. Unless you, for some reason, use hard-coded message numbers rather than the symbolic M_ constants!
(You also won't have to change anything if you were trying to work around the old system-- ids 3-254 and 261 and up are still well within the designer's space)