[Freeciv-Dev] (PR#3379) island improvement equivalence

["Mike Kaufman via RT" <rt@xxxxxxxxxxxxxx>]

here's a patch which [re]implements improvement equivalence islands.
You haven't noticed that this is missing, because the rulesets don't 
have any buildings that do this.

savegames are identical.

attached also is a savegame to show you how it works and a modified
ruleset (you'll have to modify rulesetdir in the savegame to get it to
work).

-mike

equiv_impr1.diff.gz
Description: equiv_impr1.diff.gz

improv-test.sav.gz
Description: improv-test.sav.gz

buildings.ruleset.gz
Description: buildings.ruleset.gz