-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
-Codechange: introduced ZOOM_LVL_DETAIL to show/remove details
-Codechange: changed << and >> operator with ZoomLevel to a simple wrapper (that in theory also allows zoom-in besides the current zoom-out)
-Fix r9845: missed some int -> ZoomLevel