(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.cpp

@@ -0,0 +1,24 @@
+#include "../stdafx.h"
+#include "../zoom.hpp"
+#include "../gfx.h"
+#include "../functions.h"
+#include "null.hpp"
+
+static FBlitter_Null iFBlitter_Null;
+
+void Blitter_Null::Draw(Blitter::BlitterParams *bp, BlitterMode mode, ZoomLevel zoom)
+{
+}
+
+Sprite *Blitter_Null::Encode(SpriteLoader::Sprite *sprite, Blitter::AllocatorProc *allocator)
+{
+	Sprite *dest_sprite;
+	dest_sprite = (Sprite *)allocator(sizeof(*dest_sprite));
+
+	dest_sprite->height = sprite->height;
+	dest_sprite->width  = sprite->width;
+	dest_sprite->x_offs = sprite->x_offs;
+	dest_sprite->y_offs = sprite->y_offs;
+
+	return dest_sprite;
+}