Qt client: Change the way spy action probabilities are displayed.

- Show "(?%)" in stead of a warning icon for "known to be unknown".
- Remove the text after chance value percentage on the label it self.
- Explain what the chance value percentage is in a tool tip.

See patch #4666

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24807 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Prevent taking nation that is not is_playable.

Reported by Andreas Rosdal <andreasr>

See bug #21901


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24808 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Disabled happyborders in civ2civ3 ruleset.

Patch by David Fernandez <bardo>

See patch #4642


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24810 a0f10bec-cc02-0410-94fc-a9cfff90b4cd