2.5

Safe method to move render results to the displayed image.

It now allocates a single image for display, and on each
refresh callback from render, it copies the refreshed 
section over to this image, in 32 bits. While rendering
that image then only shows progress updates, as usual.
This also now works for scenes in composte and results
for composite.

This should solve reported crashes for MBlur or SSS.

source/blender/editors/space_image/image_draw.c

@@ -121,10 +121,6 @@ static void image_verify_buffer_float(SpaceImage *sima, ImBuf *ibuf)
 			else 
 				IMB_rect_from_float(ibuf);
 		}
-		else if(sima->pad) {
-			sima->pad= 0; // XXX temp for render updates!
-			IMB_rect_from_float(ibuf);
-		}
 	}
 }