This version is quite buggy, however it is drawing hexagons to the screen
without crashing, so is being saved.
Fixed the horizontal pixel coordinate calculation.  Also removed some debugging
code.
Remove all object files upon 'make clean'.
Removed some debugging code.  Used clear_bitmap() instead of rectfill() to
clear the screen.  This buggy version still does draw hexagons.
Initialized index_of_clone properly.
Removed some debugging code.
Rendered to the frame in memory first, then rendered that to the screen.  Fixed
the computation of the frame height.
Rendered the frame to the screen only once per generation.
More debugging code.  Also, only visualize the last generation if we haven't
already done so.
Acquire the frame before trying to save it.  This successfully writes the
memory bitmap to disk.
Removed unneeded assertion.
Allocated the color_map so we can use draw_lit_sprite().
Moved the color handling from HexagonRendering to VisualizeHexPopulation.