Missing bfnt on D678

[reticulatedpines]

Newer cams don't have an embedded bitmap format font. RBF can be used in most places, but there are a few where this doesn't work. Mostly for very early debug messages, but also for some icons and menus.

Kitor implemented the ability to load a compatible bfnt from card and the font format is not complicated - converting an existing bitmap font with a compatible license is the obvious choice (and making replacement icons for those cases, similar but distinct from Canon icons).

See "bfnt read fail" in rbf_font.c

I forked a possible good font to use: https://github.com/reticulatedpines/spleen/ BDF fonts are text, and this one is BSD licensed, so we could put into our repo directly. We would need to credit the BSD code, I'm not sure where that would go (about screen? Not much space though). I made a bdf2fnt converter which could run at build, so we never need to keep large binaries in our repo.