Made several modifications to get rid of global variables in the various states.
The purpose is to make the states "reentrant".
The reasons are given in the DEVNOTES
(mapstate.c still has some global variables. I'll get to it next)
No more global variables in the map state.
Added functions to blit bitmaps in the Musl structure.
Styles are now prefixed with style$... in the musl structure after I had my first namespace collision.
The Musl interpreter now also has a CENTERTEXT function to draw text centered in the middle of the screen.
Moved DEVNOTES.txt to DEVNOTES.md and added markdown.