Fix oldreadytotele not being set in gotoroom()

This fixes a deltaframe glitch where the "- Press ENTER to Teleport -"
prompt would show up for a split second if you exited the game while the
prompt was fully faded in, and then re-entered it.

desktop_version/src/Map.cpp

@@ -887,6 +887,7 @@ void mapclass::gotoroom(int rx, int ry)
 	obj.removeallblocks();
 	game.activetele = false;
 	game.readytotele = 0;
+	game.oldreadytotele = 0;
 
 	//Ok, let's save the position of all lines on the screen
 	obj.linecrosskludge.clear();