Messages now show up again
Pull point struct into its own header
Initial draft of sprite cache code
Build instructions for sprite, point
Explicitly set draw color before blanking the screeen
Replace tile glyph concept with tile sprite concept

This is kind of half-assed, as I just changed the tile data structure,
didn't update references.  I'm pushing it now mostly so I can slurp it
donw on the laptop.  It's ok to break the build in branches, that's what
branches are for.