Added virtual functions set_pixel, get_color, fill_span and draw_drawable

Added virtual functions set_pixel, get_color, fill_span and draw_drawable

2000-11-15  Alexander Larsson  <alla@lysator.liu.se>

	* gdk/linux-fb/gdkprivate-fb.h:
	Added virtual functions set_pixel, get_color,
	fill_span and draw_drawable to the GC.
	Added global _gdk_fb_screen_gc to use instead of
	NULL when drawing to the screen.
	Added _gdk_fb_gc_calc_state() prototype.

	* gdk/linux-fb/gdkgc-fb.c:
	Call _gdk_fb_gc_calc_state() on any gc state change.

	* gdk/linux-fb/gdkglobals-fb.c:
	Add _gdk_fb_screen_gc

	* gdk/linux-fb/gdkdrawable-fb2.c:
	_gdk_fb_gc_calc_state() calculates best functions
	for the GC state and depth.
	Moved bpp specialized code to separate functions.
	Added optimized 24 bpp AA draw_drawable.

	* gdk/linux-fb/gdkevents-fb.c:
	Silence gcc warning.

	* gdk/linux-fb/gdkimage-fb.c:
	Use _gdk_fb_screen_gc

	* gdk/linux-fb/gdkwindow-fb.c:
	Init and use _gdk_fb_screen_gc

	* gdk/linux-fb/mitypes.h:
	Remove unused types.