Replaced requirement property "negated" with opposite "present"
This means that the value needs not to be double-negative.

Patch by Emmet Hikory <persia>

As this is first ruleset format change since S2_5 was branched,
also bumped capability string to make it different between branches.

See patch #3879


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@22861 a0f10bec-cc02-0410-94fc-a9cfff90b4cd