Fix for active player status when creating a new map

[ceeac]

This is somewhat related to this thread.

When starting a new map while another one with AI players activated is running, the "active player" status is not reset.
To reproduce the bug:

• Load a map with AI players active or start a new map and activate AI players
• Start a new map using the "new world" dialogue
• Save
• Close the game
• Reload previous save
• Save
• Compare the two saves

[Dwachs]

In my opinion, settings.player_active is completely useless and should be removed. The active-state of each player is stored within player_t anyway. (also settings.player_type is close to useless)

[Dwachs]

removed this variable in r9260