fix "icon alpha is 50% on WinXP". XP will use the 8 bits alpha of alpha in a 32bpp bitmap instead of the mask, so we need to keep all 8 bits around in the bitmap.

stepmania/src/archutils/Win32/WindowIcon.cpp

@@ -22,7 +22,7 @@ HICON IconFromSurface( const RageSurface *pSrcImg )
 			0x00FF0000,
 			0x0000FF00,
 			0x000000FF,
-			0x80000000 );
+			0xFF000000 );
 		RageSurfaceUtils::Blit( pSrcImg, pImg );
 	}