Change follow tag for unstable branches to branch-specific tag
("S2_6" for trunk).

See gna patch #4942.

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25584 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Updated Spanish translation by Jordi Negrevernis i Font
(this is just a copy of S2_5 r25586).
Stats on trunk:
freeciv: 81%: 5246 translated, 766 fuzzy, 485 untranslated.

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25587 a0f10bec-cc02-0410-94fc-a9cfff90b4cd