free,slabtop,uptime: complain about extra ops

free, slabtop and uptime would happily take extra command line
arguments and doing nothing about them. The programs now check
optind after option processing and will give you usage screen
if there is anything extra.

References:
 procps-ng/procps#181

free.c

@@ -341,6 +341,8 @@ int main(int argc, char **argv)
 		default:
 			usage(stderr);
 		}
+	if (optind != argc)
+	    usage(stderr);
 
 	do {