Remove a couple of unused arguments where possible, and add /* ARGSUSED */ to

the rest to reduce lint output.

cmd-pipe-pane.c

@@ -129,6 +129,7 @@ cmd_pipe_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
 	}
 }
 
+/* ARGSUSED */
 void
 cmd_pipe_pane_error_callback(
     unused struct bufferevent *bufev, unused short what, void *data)