Disable hardcoded (10,5) no-follow rule in custom levels

Scripting crewmates apparently have a specific hardcoded rule in their
follow-player code that makes it so if they're in (10,5) and are to the
left of the line x=155, they will refuse to continue following the
player. This was clearly done to make it so Vitellary in the main game
wouldn't overlap the teleporter, and that was clearly done to make it so
it wouldn't look like he would go behind the teleporter, which would
look weird (I also noticed this in #513).

I stumbled across this code and thought that just like other weird
main-game code that shouldn't apply in custom levels (#136, #137, #144),
this should be fixed, too.

desktop_version/src/Entity.cpp

@@ -2773,7 +2773,7 @@ bool entityclass::updateentities( int i )
                 }
 
                 //Special rules:
-                if (game.roomx == 110 && game.roomy == 105)
+                if (game.roomx == 110 && game.roomy == 105 && !map.custommode)
                 {
                     if (entities[i].xp < 155)
                     {