Let ejabberdctl accept binary string arguments

Don't print the following message if an ejabberd command expects binary
string arguments: "This command cannot be executed using ejabberdctl.
Try ejabberd_xmlrpc."

src/ejabberd_ctl.erl

@@ -418,6 +418,7 @@ is_supported_args(Args) ->
       fun({_Name, Format}) ->
 	      (Format == integer)
 		  or (Format == string)
+		      or (Format == binary)
       end,
       Args).