(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/openttd.cpp

@@ -402,6 +402,7 @@ int ttd_main(int argc, char *argv[])
 			strcpy(musicdriver, "null");
 			strcpy(sounddriver, "null");
 			strcpy(videodriver, "dedicated");
+			strcpy(blitter, "null");
 			dedicated = true;
 			if (mgo.opt != NULL) {
 				/* Use the existing method for parsing (openttd -n).