Fixed the Encore mode invert wipe.

Explanation: NearestColor takes UINT8 inputs, but is being provided a number in the range of 1 to 256(!!) - which means very dark channels were looping back around to 0.

This error might exist in public branches too, because I don't think Encore's wipes would have been changed internally without us knowing.

src/v_video.c

@@ -1517,9 +1517,9 @@ void V_EncoreInvertScreen(void)
 		for (; buf < deststop; ++buf)
 		{
 			*buf = NearestColor(
-				256 - pLocalPalette[*buf].s.red,
-				256 - pLocalPalette[*buf].s.green,
-				256 - pLocalPalette[*buf].s.blue
+				255 - pLocalPalette[*buf].s.red,
+				255 - pLocalPalette[*buf].s.green,
+				255 - pLocalPalette[*buf].s.blue
 			);
 		}
 	}