This patch implements a way for minimap-type GUI objects to request the rendering
of the minimap texture each frame. If it wasn't requested the minimap
texture isn't rendered at all and the objects only request it while they are
being displayed. This saves unnecessary work and fixes a bug where the
minimap briefly showed the revealed map after a cinema path ended
playing, since it isn't updated every frame (only 2x per second).
01476b9836