Window peep & Sprite/Ride List modification

I meant to split this into two branches but made a mistake. I've started implementing window_peep but it is not even remotely close to finished. Only the open function has been written. 
I've also tried a different way of doing the global sprite and ride lists. With the new setup there is no need to use RCT2_ADDRESS and its all in a single global var g_ride_list and g_sprite_list.