[New Feature] Save the last played Skirmish map to `SUN.INI`.

[CCHyper]

Description:

Save the last played Skirmish/Multiplayer map so it can be the initially selected map on the next game start. Currently Tiberian Sun always resets to the first map listed in the map list.

Possible Implementation:

Store this new value in SUN.INI under [MultiPlayer].

Possible Enhacement:

Setting this new value to -1 would randomise the initial map selection process.