(svn r10092) -Codechange: code-seperated the spriteloader and blitter from the rest of the code

-Add: make it possible to pick your own blitter (-b <blitter>, -h for overview)
-Add: added a new optimized 8bpp blitter (default, caches sprites of all zoom-levels)
-Add: added a debug 8bpp blitter and a very slow normal 8bpp blitter

src/spriteloader/grf.hpp

@@ -0,0 +1,18 @@
+/* $Id$ */
+
+/** @file grf.hpp */
+
+#ifndef SPRITELOADER_GRF_HPP
+#define SPRITELOADER_GRF_HPP
+
+#include "spriteloader.hpp"
+
+class SpriteLoaderGrf : public SpriteLoader {
+public:
+	/**
+	 * Load a sprite from the disk and return a sprite struct which is the same for all loaders.
+	 */
+	bool LoadSprite(SpriteLoader::Sprite *sprite, uint32 file_pos);
+};
+
+#endif /* SPRITELOADER_GRF_HPP */