Add info about -q|--quiet option

cluster/maco.check.update.sh

@@ -42,7 +42,7 @@ readonly MACO_TMP_URGENT_FILE="/tmp/.maco.urgent.upgrade"
 usage() {                                                       # {{{
 
 	cat <<- EOF
-usage: $PROGNAME [-d|-h|-s]
+usage: $PROGNAME [-d|-h|-s|-q]
 
 Compare current version of Maco script with the latest and
  the urgent versions then try to prepare the host by:
@@ -61,6 +61,9 @@ OPTIONS :
 
     -s,--simulate
         Only display messages and don't manage temp files.
+
+    -q,--quiet
+        Disable messages on standard output (except for error).
 EOF