[1.0.7.9] Warlord's Throne bonus doesn't Scale with Game Speed

[Sjaandi]

On all game speeds, the Warlord's throne still only applies a 20% production boost for 5 turns. This is equivalent to one turn of free production, which doesn't scale well, especially at marathon speed, where each turn is worth only 1/3 of an standard game. To get the same boost on marathon, the bonus should be either 20% boost for 15 turns, or 60% boost for 5 turns.