Incomplete intermediate commit, working on polar coordinate framebuffer.
Small tweak to reduce the visible impact of lost packets on the nRF24L01+ wireless.
Add simple testing of the polar coordinate framebuffer.

Fix some misc. bugs, though there are still some bugs left.
Fix bug in bm_scanline_tri12() when the passed in angle is negative.

Also add another tri framebuffer test image. Tri framebuffer seems to work
now!