Disallow rushing for victory buildings

[joseasoler]

Buildings that are part of a victory condition should not be allowed to be rushed by either money or population.

This should be implemented as a new XML tag for buildings.

[lfgr]

You have to make sure you undo this

[joseasoler]

Good point! I'll bear that in mind, thanks :)

[joseasoler]

Implementing this change is easier than I thought. There is already a bVictoryBuilding tag, currently used only by the AI. It should be simple to just use the isVictoryBuilding method at CvCity::canHurryBuilding to prevent hurrying, and to add code to CvGameTextMgr.cpp to show in the civilopedia which buildings cannot be rushed and why. Besides this, the code should also include a revert of what lfgr mentioned.