(svn r10121) -Codechange: split renderer from rest of code; no longer any code directly accesses the video-buffer

-Add: added NULL blitter and renderer, which are always used for -vnull
-Add: dedicated driver doesn't blit nor render by default. Can be overruled by user. (-D -b 8bpp-optimized)
-Remove: removed CTRL+D from win32, which is incompatible with above
-Add: extended screenshot support for PNG and BMP
-Codechange: remove all hardcoded 8bpp references and replace them with more dynamic ones
-Codechange: minor stuff in blitters

src/blitter/null.hpp

@@ -0,0 +1,30 @@
+/* $Id$ */
+
+/** @file null.hpp */
+
+#ifndef BLITTER_NULL_HPP
+#define BLITTER_NULL_HPP
+
+#include "blitter.hpp"
+
+class Blitter_Null : public Blitter {
+public:
+	/* virtual */ uint8 GetScreenDepth() { return 0; }
+
+	/* virtual */ void Draw(Blitter::BlitterParams *bp, BlitterMode mode, ZoomLevel zoom);
+
+	/* virtual */ Sprite *Encode(SpriteLoader::Sprite *sprite, Blitter::AllocatorProc *allocator);
+
+	/* virtual */ const char *GetRenderer() { return "null"; }
+};
+
+class FBlitter_Null: public BlitterFactory<FBlitter_Null> {
+public:
+	/* virtual */ const char *GetName() { return "null"; }
+
+	/* virtual */ const char *GetDescription() { return "Null Blitter (does nothing)"; }
+
+	/* virtual */ Blitter *CreateInstance() { return new Blitter_Null(); }
+};
+
+#endif /* BLITTER_NULL_HPP */