[freeciv-ai] [Patch] Cleanup of process_*_want [1.6]

[Gregory Berkolaiko <Gregory.Berkolaiko@xxxxxxxxxxxx>]

I took Petr's patch, updated it and made some changes, mostly comments.  
Also converted an if - esle if - else if - else to switch.

Tested savegames, they are identical.  Highly recommended for inclusion 
(yeah, yeah, feature freeze, but it's not a feature, it's cleanup, long 
due for inclusion, good quality and will undoubtedly be forgotten after 
the release, so please include). 

Best wishes,
G.