Thread ai workers calculate tile improvement value differently depending on
whether tile is currently being worked by the city or not.
For already worked tiles, we look for greatest delta (improvement to
city). For future tiles we look for having greatest total output from
the tile we're going to work next. Also consider the case where we can
improve not-worked tile to be better than worst currently-worked tile,
so it would make sense to move the city worker.

See patch #4952


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25613 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Remove the now unused fields REQ_RANGE and REQ_TYPE from packets.def

See patch #4962

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25614 a0f10bec-cc02-0410-94fc-a9cfff90b4cd