Made Sun Tzu's War Academy to apply to Big Land units in civ2civ3 ruleset.

Patch by David Fernandez <bardo>

See patch #4640


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24783 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Requirements with Adjacent/CAdjacent ranges always check the centre tile too.
Fixed the TerrainClass, Extra, TerrainFlag, BaseFlag, RoadFlag, CityTile,
and MaxUnitsOnTile requirements.
Also, TerrainClass/TerrainFlag City-ranged requirements now cope with
unknown terrain within the city radius.

See gna bug #21470.

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24785 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Check for activities of the settler-type units in the adjacent tiles when
another activity potentially removing requirement for it is finished.
This used to be hardcoded so that only finishing mining, and thus potentially
removing irrigation conflicting with the mine, caused recheck of adjacent units
building irrigation.

See patch #4656


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24788 a0f10bec-cc02-0410-94fc-a9cfff90b4cd