ntpd: add -S PROG option. This feature is crucial for CMOS/RTC syncronization

function                                             old     new   delta
run_script                                           112     278    +166
ntpd_main                                            779     825     +46
update_local_clock                                   824     858     +34
packed_usage                                       26518   26540     +22
ntp_init                                             366     371      +5
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(add/remove: 0/0 grow/shrink: 5/0 up/down: 273/0)             Total: 273 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/usage.h b/include/usage.h
index 8c5a2db..c5707d8 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -3226,7 +3226,7 @@
        "Address:    127.0.0.1\n"
 
 #define ntpd_trivial_usage \
-	"[-dnqwl] [-p PEER]..."
+	"[-dnqwl] [-S PROG] [-p PEER]..."
 #define ntpd_full_usage "\n\n" \
        "NTP client/server\n" \
      "\nOptions:" \
@@ -3238,6 +3238,7 @@
 /*   "\n	-N	Run at high priority" */ \
      "\n	-w	Do not set time (only query peers), implies -n" \
      "\n	-l	Run as server on port 123" \
+     "\n	-S PROG	Run PROG after stepping time, stratum change, and every 11 mins" \
      "\n	-p PEER	Obtain time from PEER (may be repeated)" \
 
 #define od_trivial_usage \