*: 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/libbb/getopt32.c b/libbb/getopt32.c
index 9e53dfd..51e0306 100644
--- a/libbb/getopt32.c
+++ b/libbb/getopt32.c
@@ -117,7 +117,7 @@
         if w is given once, GNU ps sets the width to 132,
         if w is given more than once, it is "unlimited"
 
-        int w_counter = 0;
+        int w_counter = 0; // must be initialized!
         opt_complementary = "ww";
         getopt32(argv, "w", &w_counter);
         if (w_counter)
@@ -220,7 +220,7 @@
  "x--x" Variation of the above, it means that -x option should occur
         at most once.
 
- "a+:"  A plus after a char in opt_complementary means that the parameter
+ "a+"   A plus after a char in opt_complementary means that the parameter
         for this option is a nonnegative integer. It will be processed
         with xatoi_u() - allowed range is 0..INT_MAX.
 
@@ -255,7 +255,7 @@
         For example from "id" applet:
 
         // Don't allow -n -r -rn -ug -rug -nug -rnug
-        opt_complementary = "r?ug:n?ug:?u--g:g--u";
+        opt_complementary = "r?ug:n?ug:u--g:g--u";
         flags = getopt32(argv, "rnug");
 
         This example allowed only:
@@ -545,11 +545,14 @@
 		if (on_off->counter)
 			(*(on_off->counter))++;
 		if (on_off->param_type == PARAM_LIST) {
-			llist_add_to_end((llist_t **)(on_off->optarg), optarg);
+			if (optarg)
+				llist_add_to_end((llist_t **)(on_off->optarg), optarg);
 		} else if (on_off->param_type == PARAM_INT) {
-			*(unsigned*)(on_off->optarg) = xatoi_u(optarg);
+			if (optarg)
+				*(unsigned*)(on_off->optarg) = xatoi_u(optarg);
 		} else if (on_off->optarg) {
-			*(char **)(on_off->optarg) = optarg;
+			if (optarg)
+				*(char **)(on_off->optarg) = optarg;
 		}
 		if (pargv != NULL)
 			break;