*: shrink: use Vladimir's "o+" specifier instead of xatou(opt_param)

function                                             old     new   delta
getopt32                                            1370    1385     +15
sulogin_main                                         490     494      +4
realpath_main                                         84      86      +2
sleep_main                                            76      77      +1
mt_main                                              256     257      +1
printenv_main                                         75      74      -1
fdformat_main                                        546     545      -1
usleep_main                                           44      42      -2
setlogcons_main                                       77      75      -2
ed_main                                             2654    2649      -5
deallocvt_main                                        69      64      -5
addgroup_main                                        373     368      -5
mkfs_minix_main                                     2989    2982      -7
tail_main                                           1221    1213      -8
sv_main                                             1254    1241     -13
du_main                                              348     328     -20
tftp_main                                            325     302     -23
split_main                                           581     558     -23
nc_main                                             1000     977     -23
diff_main                                            891     868     -23
arping_main                                         1797    1770     -27
ls_main                                              893     847     -46
od_main                                             2797    2750     -47
readprofile_main                                    1944    1895     -49
tcpudpsvd_main                                      1973    1922     -51
udhcpc_main                                         2590    2513     -77
grep_main                                            824     722    -102
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/22 up/down: 23/-560)         Total: -537 bytes
   text    data     bss     dec     hex filename
 796973     658    7428  805059   c48c3 busybox_old
 796479     662    7420  804561   c46d1 busybox_unstripped

diff --git a/coreutils/tail.c b/coreutils/tail.c
index 52aa8f6..35b25a4 100644
--- a/coreutils/tail.c
+++ b/coreutils/tail.c
@@ -87,7 +87,6 @@
 	bool from_top;
 	int header_threshhold = 1;
 	const char *str_c, *str_n;
-	USE_FEATURE_FANCY_TAIL(const char *str_s;)
 
 	char *tailbuf;
 	size_t tailbufsize;
@@ -110,8 +109,9 @@
 	}
 #endif
 
+	USE_FEATURE_FANCY_TAIL(opt_complementary = "s+";) /* -s N */
 	opt = getopt32(argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"),
-			&str_c, &str_n USE_FEATURE_FANCY_TAIL(,&str_s));
+			&str_c, &str_n USE_FEATURE_FANCY_TAIL(,&sleep_period));
 #define FOLLOW (opt & 0x1)
 #define COUNT_BYTES (opt & 0x2)
 	//if (opt & 0x1) // -f
@@ -119,7 +119,6 @@
 	if (opt & 0x4) count = eat_num(str_n); // -n
 #if ENABLE_FEATURE_FANCY_TAIL
 	if (opt & 0x8) header_threshhold = INT_MAX; // -q
-	if (opt & 0x10) sleep_period = xatou(str_s); // -s
 	if (opt & 0x20) header_threshhold = 0; // -v
 #endif
 	argc -= optind;