Added alternate teleport algorithm. Though none of two work properly.
Semi-fixed player backflip glitches.

An attempt to mark ridden cart as dead results in that entity being silently deleted from loaded entities list before entities update tick ends. This goes to IndexOutOfBoundsException. The strange thing is that non-ridden entities work just fine.
Refactored teleport code into something much more compact. The trouble with minecarts persists. Arrgh.
Some changes in mount handling