(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/8bpp_simple.hpp

@@ -7,15 +7,15 @@
 
 #include "blitter.hpp"
 
-typedef Pixel Pixel8;
-
 class Blitter_8bppSimple : public Blitter {
 public:
-	uint8 GetScreenDepth() { return 8; }
+	/* virtual */ uint8 GetScreenDepth() { return 8; }
 
-	void Draw(Blitter::BlitterParams *bp, BlitterMode mode, ZoomLevel zoom);
+	/* virtual */ void Draw(Blitter::BlitterParams *bp, BlitterMode mode, ZoomLevel zoom);
 
-	Sprite *Encode(SpriteLoader::Sprite *sprite, Blitter::AllocatorProc *allocator);
+	/* virtual */ Sprite *Encode(SpriteLoader::Sprite *sprite, Blitter::AllocatorProc *allocator);
+
+	/* virtual */ const char *GetRenderer() { return "8bpp"; }
 };
 
 class FBlitter_8bppSimple: public BlitterFactory<FBlitter_8bppSimple> {