[Freeciv-Dev] (PR#8754) effects patch

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=8754 >

And these variables:

common/improvement.h:extern int B_CAPITAL_CITY, B_LAND_DEFEND;

shouldn't be all-capitalized (they are variables, not macros), nor do
they need a B_ prefix.  And we really don't need more global variables.
 They should just be added to the game struct as game.palace_building
and game.land_defend_building.

jason