Option to show unexplored secret lindefs only w/ am_cheat

[Abba Zabba]

I like the automap customization quite a bit, but I normally turn the am_map_secrets to 1 instead of 2 because it displays unexplored secret colors by default with no cheats enabled if set to 2. With an option to enable the unexplored secret color definition only when using iddt or am_cheat, the map relays more information when you want it to, instead of always being on and thus cheating with normal use.