void heart_beat()

This function will be called automatically every 2 seconds. The start and
stop of heart beat is controlled by set_heart_beat().

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

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.

The function this_player() will return this object, but only if it is living.
Otherwise, this_player() will return 0.

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