Add all attacking units at battle site for retreat consideration

[ron-murhammer]

Fixes #442.

Need to consider units such as infra that were removed from fighting in the battle when retreating.

[DanVanAtta]

Looks good. I tested this on BW v3, Feudal Japan and Domination 1914 No mans land.
Feudal Japan is where we saw the problem, horses would be given away if you attacked with them and retreated. That no longer happens with this branch, horses retreat with the attacking army.

Nice work finding the fix for this @ron-murhammer , that ticket (#442) has been open for some time.

[panguitch]

Yes, thanks @ron-murhammer, just tested this for Greyhawk Wars and looks good. This will allow me to delete the "hack" support attachment that enabled bowmen to retreat. And when they retreat if you brought troops from multiple territories the bowmen can choose which territory to retreat to, not just the one they came from--which is as it should be and I'm glad to see it work that way since I could see that nuance getting lost.

I do notice that it no longer shows AA units in the battle window the way it used to. Not really a problem but it's a little weird since it shows their rolls against attacking aircraft but doesn't show them. Not sure if this was part of the fix or a side effect.

[ron-murhammer]

@panguitch This change shouldn't have any effect on what units display in the battle window since all it does is add infra units to the possible units to consider for retreat. If you test a version right before this change then you should see the same issue. Feel free to open an issue for it and what version you've tested that have or don't have the problem.

[panguitch]

Nevermind. Can't recreate this problem in the release where I first saw it, so I must have been imagining things to begin with!