Only allow builders to guard out of map

[saurtron]

Work done

• Add rule to only allow builders to guard other units out of map.

Addresses Issue(s)

• Constuction aircraft cannot be assisted if aircraft outside of map #763

This doesn't fix the issue directly, but once engine version with out of map leniency hits it will be fixed, this PR addresses concerns at the issue of avoiding aircraft guard hacks out of map.

out of map leniency is removing restrictions on out of map guard and attack (except for ground attack).

Test steps

• Make an aircraft builder build something close to the edge.
• Wait until it's out of map.
• Set some other unit, like another air con to guard it.

Remarks

• This goes in unit_prevent_aircraft_hax.lua. It does affect other units since for example construction turrets can help airplanes too. It's all about preventing aircraft hacks so I think it's ok.
• This only will really have an effect with latest engine version, but it won't hurt if run with an older (like current) version, it will just enforce something the engine is also enforcing itself.