* Split the big mui.h header into smaller headers. It was just getting too big really.
* Removed *incbin.h* -- this was incompatible with several linkers, and didn't work for webassemly. Now the fonts are just included as C arrays.
* Introduced a new *mui_control_group*. Basically the list of control is now made of (optional) multiple groups. A normal window only uses one, but for tab controls for example, that'll be quite handy.
* This introduces a new API to iterate the window/control list, you can selectively iterate all, or just the visible controls.
* There is now a standard PUT file dialog, with a "New" folder button and all.
* Added an optional close box to the window title bars.
