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.
When player move fast enough, tiles update for specific area square
couldn't catch player move. Tiles to be removed are left in the queue
with lower priority then tiles to be added which are nearest to player.
This can lead to overflow for amount of tiles. So we try to do remove
first. But we detect change type approximately using mixed change type,
because even if we do it precise, change type could change while job
is in queue.
elsid