*: remove some uses of argc

function                                             old     new   delta
whoami_main                                           34      37      +3
logname_main                                          60      63      +3
hostid_main                                           35      38      +3
ttysize_main                                         136     135      -1
nmeter_main                                          673     672      -1
logger_main                                          387     386      -1
uuencode_main                                        330     328      -2
ifupdown_main                                       2125    2123      -2
mesg_main                                            158     155      -3
free_main                                            333     330      -3
cal_main                                             902     899      -3
acpid_main                                           443     440      -3
ar_main                                              196     189      -7
find_main                                            476     467      -9
ifconfig_main                                       1235    1221     -14
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/12 up/down: 9/-49)            Total: -40 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/miscutils/readahead.c b/miscutils/readahead.c
index fb71ce8..f3b21a2 100644
--- a/miscutils/readahead.c
+++ b/miscutils/readahead.c
@@ -13,11 +13,13 @@
 #include "libbb.h"
 
 int readahead_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int readahead_main(int argc, char **argv)
+int readahead_main(int argc UNUSED_PARAM, char **argv)
 {
 	int retval = EXIT_SUCCESS;
 
-	if (argc == 1) bb_show_usage();
+	if (!argv[1]) {
+		bb_show_usage();
+	}
 
 	while (*++argv) {
 		int fd = open_or_warn(*argv, O_RDONLY);