- cleanup of savegame picture code.

* re-added screen blends for images from the hardware renderer.
* moved all postprocessing of the image out of the renderers.
* cleaned out a large piece of cruft for handling the palette in the frame buffer class. This was all a remnant of the old paletted backend that no longer exists. Nowadays the screen blend is just a postprocessing effect drawn over the 3D screen, there is no need to maintain any of it as global state anymore.
* since the engine doesn't produce paletted screenshots anymore there is no need to have handling for it in the generation code. This depended on otherwise obsolete information so it got removed along with that information.

src/d_main.cpp

@@ -1247,7 +1247,6 @@ void D_DoAdvanceDemo (void)
 		return;
 	}
 
-	V_SetBlend (0,0,0,0);
 	players[consoleplayer].playerstate = PST_LIVE;	// not reborn
 	usergame = false;				// no save / end game here
 	paused = 0;
@@ -2698,8 +2697,6 @@ void D_DoomMain (void)
 		}
 		else
 		{
-			// let the renderer reinitialize some stuff if needed
-			screen->InitPalette();
 			// These calls from inside V_Init2 are still necessary
 			C_NewModeAdjust();
 			D_StartTitle ();				// start up intro loop