[RA] Formations not available in Skirmish mode

[Gerwin2k]

Formations work in normal single player mode.
Make a team, hit the F key. Team number and 'F' are written in the unit selection outlines.
In skirmish mode the F key does nothing. May be the same for Multiplayer, but I did not test this.

Possible fix, or at least a workaround, can be made in conquer.cpp. By replacing obj->IsSelected with obj->Is_Selected_By_Player()) three times = all occurences. I don't know why this works, but ended up with this solution with some trouble-shooting and by looking at the similar team formation code.

void Toggle_Formation(void)
...
if (obj && !obj->IsInLimbo && obj->House == PlayerPtr && obj->Is_Selected_By_Player()) { // GB 2024, replaced  obj->IsSelected
...