This patch is a follow-up to D3297/rP24539.
Currently all arrow-shooting structures have the same reload time (2 s), the same nominal maximum range (60), and the same number of additional arrows per garrisoning soldier (1). However, the damage-per-arrow values vary greatly:
```
wall tower: 8
small tower: 9
large tower: 12
civic centres: 12
fortress: 16
army camp: 25
```
This patch does the following:
* all these structures now inflict the same damage per arrow, which is standardized to 10 pierce (i.e. 5 per second and per soldier);
* to compensate for that, the new default arrow counts are:
```
wall tower: 0
small tower: 1
large tower: 1→2
civic centres: 3
fortress: 3→4
army camp: 1→3
```
* to compensate for the higher default arrow count of large towers, the `tower_watch` technology (“Sentries”, which raised the default arrow count by 1) is deleted;
* while at it, removed the lower resistances of the small tower, giving them the same values as other towers; their health is lowered accordingly, by 20% (i.e. 500→400); the difference for crush damage is negligible (500×0.9^2=405); the main advantage is that it makes comparing towers much easier.
As a consequence of these changes, civic centres and fortresses are somewhat less dangerous and garrisoning defensive structures is less effective at killing attackers.
See also D2854.