[PATCH] Take account of control group when checking if we can upgrade an entity.

[fatherbushido]

Attached patch:

• takes into account the control group when checking placement before an upgrade
• uses a new function to avoid duplication
• fixes (?) a call to an unknown function

I join also a patch using that for wall towers wich could fix nicely #3811 (screenshot) following an idea of FeXor and Mythos_Ruler (in 3 years ago discussions on the forum).

[fatherbushido]

more accurate strings are not included

[fatherbushido]

In the wall turret patch there is only the macedonian walls. Stuff should be done carefully (celtic wall towers, look at roman siege walls too) but I wait if the approach is good.

[fatherbushido]

In 18878:

Take account of control group when checking if we can upgrade an entity. Fix a call to an unknown function. Style reviewed by elexis, logic overviewed by wraitii. Fix #4285.