[PATCH] Exploit nomad: make cc for opponent unbuildable during ceasefire

[ffm]

reproduce: In unknown nomad, send the cavalry to scout. See enemy placing a foundation and go quick on it and press stop button.

The enemy can't move your cavalry and is forced to wait until he can attack it.

During war the enemy shouldn't make way for foundations (for example let a wall be build), but in this case the cavalry (or any unit) should leave the foundation.

This can be prevented on the player side, if the foundation is near your units so the construction starts fast and far from enemy units.

[leper]

You can also destroy the foundation and place it anew.

[elexis]

See the reopening of #3132 and r16574

[mimo]

I guess it would be enough to replace in line 210 of UnitAI.js

if (Not IsOwnedByAllyOfEntity

...

by

if ((Not IsOwnedByAllyOfEntity && Not underCeaseFire)

...

[Sandarac]

As per mimo's suggestion.

[mimo]

In 18488:

apply leaveFoundation to enemies when under ceaseFire, fixes #3667, patch by Sandarac

[mimo]

Thanks for the patch (I've inlined isCeaseFire as only used once).