Haitian Pro-Aristide Marchers Threaten PM PORT-AU-PRINCE, Haiti - Machete-wielding supporters of ousted President Jean-Bertrand Aristide are turning their wrath on Haiti's demoralized police force, beheading some of their victims in a campaign imitative of the insurgency in Iraq.    Seven of at least 18 people killed in the turmoil in Port-au-Prince have been police officers, judicial police chief Michael Lucius said Monday...