[Freeciv-Dev] (PR#13475) ai_choice needs documentation

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=13475 >

The ai_choice struct needs some documentation.  It's declared in city.h
for some reason, but there is no explanation of what values are posible
for each field or what they might mean.  This makes it impossible to use
unless you spend a lot of time figuring out how it works.

-jason