The previous code did not work when the list did not start at index 0
of the inventory list (issue #779).

The 50 ms delay causes frequent test failures on certain systems with
slow network stacks, these failures go away with the 100 ms variant.

Play player_damage.ogg when recieving damage and additionally play player_falling_damage.ogg when recieving falling damage

This reverts commit 649dca4d.

Now Environment::clearAllObjects() unloads unused blocks in an interval
defined by max_clearobjects_extra_loaded_blocks (default 4096).