Save buildings.ruleset from freeciv-ruledit

See patch #4352


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@23900 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Avoid using gtk_combo_box_new_with_model_and_entry() in Gtk2 nation
picker, since this was only added in Gtk 2.24 and we claim to be
compatible with 2.12.

Reported by Jordi Negrevernis i Font (jorneg@gna).

See gna bug #21371.

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@23901 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Restrict online help to nations in current nationset once the game has
started.

See gna patch #4354.

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@23902 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Show modpack notes as tooltip in Qt modpack installer

See patch #4353


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@23905 a0f10bec-cc02-0410-94fc-a9cfff90b4cd