Added in extra "maptype" value for each call to resetMap
Fix for zoom map bug

Added in an extra height map cache; very small, shouldn't really affect
memory or performance
Added necessary references to decide which cache to use
Added the mapType integer to determine which cache to store data in
Removed the little_big_heightmap

I think this is a better solution. That second height map array may have
some unintended consequences so I got rid of it. Now the heightmap is
only referred to when generating the big map, not the zoom map.
Merge branch 'master' into v6