Lfun:	heart_beat - the heart beat of a living

Synopsis:
	void heart_beat()

Description:
	This function will be called automatically every 2 seconds if the
	object is living. The start and stop of the heart beat is controlled
	by the set_heart_beat efun.

	Be careful not to have objects with heart beat running all the time,
	for it uses a lot of resources.

	All monsters turn off their heart_beat after a while if no player is
	present. See test_if_any_here for more information.

	If there is an error in the heart beat routine, the heart beat will be
	turned off until this object is recompiled, and can not be restarted
	with set_heart_beat.

	Inside the heart_beat routine, the function this_player will return
	the current object, but only if it is living. Otherwise, this_player()
	will return 0.

Return value: ignored

Examples:
	There are some examples for heart_beat in the game. Tell me to mention
	some here, when you read this - Junky.

See also: efun/set_heart_beat, efun/call_out, efun/enable_commands