* two new types of aliens. only one rules.
  * removed gfx_write in favor of gfx_putchar and gfx_putstr.
  * added bonuses at alien death. they do nothing yet.
  * seeker missiles. 'b' to test.
  * weapon resolution is now 16*char. needs to be generalized.
  * fixed the supernova bugs. center could collide with the tunnel, and
    the last frame was badly displayed.
  * lots of cleanups everywhere.


git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/ttyvaders/trunk@20 92316355-f0b4-4df1-b90c-862c8a59935f