Freeciv

In http://forum.freeciv.org/f/viewtopic.php?f=11&t=91310, user "Voland0" is confused by the inability to build farmland on bare desert.

This is deliberate, but is a fiddly corner case that didn't seem worth documenting at the time. However, the autogenerated help for Desert does now have an inviting "Build as irrigation [Farmland] 5 turns" at the top, which probably deserves qualification.

I don't think we can improve the autogeneration in this case -- it is possible to build Farmland on desert, just only if river or oasis is present. So I don't think we can reasonably remove the "Build as irrigation [Farmland]" bit.

• To Desert, explaining that farmland can't improve bare desert.
• To Farmland, explaining that it is no help if the irrigated terrain doesn't already yield 2 food. (Which is true of most rulesets, so I've added it to them all, reducing string divergence. It's only civ2civ3 and derivatives where it causes an active detriment so we've actively prevented it; in other rulesets it's just a waste of effort.)