The api says that the user_silentkill() "Kills a user without a message.", that means it is just user_kill() without sending deathmsg.
But user_silentkill() automatically kills player without affecting the client's score (and that is not mentioned in api), so i'll add a second parameter to user_silnetkill() to let user to decide if he want to kill a player without or not affecting the table.
New parameter has the default value 1, so it won't break the compatibility.
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