Incorporated lots of fixes and suggestions from Bruce and changes to

Incorporated lots of fixes and suggestions from Bruce and changes to
facilitate the new saver loading/unloading notification interface
in syscons.

daemon_saver:
- M_NOWAIT was wrong, since NULL returns are not handled.  Just use
  M_WAITOK.
- use `ostype' instead of hard-coded "FreeBSD". Now there is no more
  hard-coded string! (But, who will run this screen saver on other
  OS?!)
- put macros and data declarations in a consistent order.
- -DDEAMON_ONLY and -DSHOW_HOSTNAME options added in the previous commit
  are removed. Options of this kind can go stale and no one notices
  because no one uses them. DEAMON_ONLY is just removed. SHOW_HOSTNAME
  is made default.

snake_saver:
- use `ostype' and `osrelease' as in the daemon saver. The string changes
  slightly - there was a hyphen after "FreeBSD"; now there is a space.
  (It is consistent with uname -a, like the daemon server already is.)

all screen savers:
- Use the new add_scrn_saver()/remove_scrn_saver() in syscons.c
  to declare loading/unloading of a screen saver. Removed reference
  to `current_saver' and the variable `old_saver' as they are not
  necessary anymore.
- The blank, fade and green screen savers manipulate VGA registers.
  Module loading should fail for non-VGA cards.
- `scrn_blanked' is consistently treated as a number/counter rather
  than boolean.
- Some savers touch `scp->start' and `scp->end' to force entire screen
  update when stopping themselves. This is unnecessary now because
  syscons.c takes care of that.
- cleared up many unused or unnecessary #include statements.
- Removed -DLKM from Makefiles.

YOU NEED TO RECOMPILE BOTH SCREEN SAVERS AND KERNEL AS OF THIS CHANGE.