video: first signs of life

The video code now writes out a bmp file per-frame. With this patch
applied, the Nintendo logo is rendered in each frame.

There is still plenty of work to be done. Pretty much everything is
hardcoded to make the bootrom work.

src/apps/gbdb.c

@@ -88,7 +88,7 @@ static void init(void)
 	cpu_ops.undef_d3 = breakpoint_cb;
 
 	lr35902_init(&cpu, memory, &cpu_ops);
-	gb_video_init(&video);
+	gb_video_init(&video, memory);
 	gb_mem_init(memory, &video);
 }