gamemode(teleporter): Set gamestate to GAMEMODE

This makes it so gamemode(teleporter) will always do an animation, even
if the game is already in TELEPORTERMODE.

I used this script to test:

    gamemode(teleporter)
    delay(5)
    gamemode(teleporter)
    delay(5)
    gamemode(teleporter)

In 2.2, this script starts the map menu bringing-up animation three
times.

In previous 2.3, this script starts the map menu bringing-up animation
once, but then the next gamemode(teleporter) immediately finishes the
animation, and the third gamemode(teleporter) does nothing.

This commit restores it to 2.2 behavior.

desktop_version/src/Script.cpp

@@ -1115,6 +1115,7 @@ void scriptclass::run(void)
 			{
 				if (words[1] == "teleporter")
 				{
+					game.gamestate = GAMEMODE; /* to set prevgamestate */
 					game.mapmenuchange(TELEPORTERMODE, false);
 
 					game.useteleporter = false; //good heavens don't actually use it