Freeciv

Currently, it's said in many places in the code and rulesets that spaceship parts should not have any other effects than SS_*. But they naturally should allow the effect Building_Buy_Cost_Pct that probably does not break anything but it should be narrated this way.
Also, the function building_has_effect() and how it works in the rulesets maybe needs redesign since it breaks the clear system of effects and requirements that we generally have. Maybe we'd better list them in a table somewhere like

[spaceship]
spaceship_parts = {"type", "buildings" 
 "Component", "Space Component" 
 "Structure", "Space Structural" 
 "Module", "Space Module"}

and put on rssanity.c the list of effects that they may or may not have (of course being sure that he former work).