Fix size mismatch warning in top-level component wiring.
First working version of bitmap renderer.

To be used for title and game over screen. Right now, the
start screen is only a displaced "game over" text, the real
graphics have yet to be made.
Updated top-level testbench for new buttons/switches.
Actually make the testbench clock 40 MHz.

Due to a misplaced comma, it was 4 MHz instead.