Do not clear value of the improvement or tech completely when evaluating single
effect that has no value.

See bug #22363


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25687 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Fixed specialist rotation in gtk3-client

See bug #22366


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25690 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Corrected comment about identity number wrapping point.

Reported by akfaew


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25693 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Silenced warnings when loading savegame saved with ruleset version that didn't
have nationality enabled but now has.

See bug #22360


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25694 a0f10bec-cc02-0410-94fc-a9cfff90b4cd