To reduce cache size and make it more flexible.
Adding off mesh connections to the navmesh is the last step of navmesh
generation and it's very fast comparing to other steps (microseconds vs
milliseconds). Having less cache size makes get and set operations almost 2x
times faster that also have an order of microseconds. So in total there is
no performance impact.
Use LRU modification to hold currently used items. Use RecastMesh binary
data for item key.
Store original pointer of btCollisionShape in user pointer to make available
it as an identifier within all duplicates. Use pointer to heights data array
for btHeightfieldTerrainShape.
