Fix usage message not mentioning v5.0.

Closes #1713. Thanks to whnr.

ChangeLog.txt

@@ -1,3 +1,7 @@
+Broker:
+- Fix usage message only mentioning v3.1.1. Closes #1713.
+
+
 1.6.10 - 2020-05-25
 ===================
 

src/conf.c

@@ -356,7 +356,7 @@ void config__cleanup(struct mosquitto__config *config)
 static void print_usage(void)
 {
 	printf("mosquitto version %s\n\n", VERSION);
-	printf("mosquitto is an MQTT v3.1.1 broker.\n\n");
+	printf("mosquitto is an MQTT v5.0/v3.1.1/v3.1 broker.\n\n");
 	printf("Usage: mosquitto [-c config_file] [-d] [-h] [-p port]\n\n");
 	printf(" -c : specify the broker config file.\n");
 	printf(" -d : put the broker into the background after starting.\n");
@@ -365,7 +365,7 @@ static void print_usage(void)
 	printf("      Not recommended in conjunction with the -c option.\n");
 	printf(" -v : verbose mode - enable all logging types. This overrides\n");
 	printf("      any logging options given in the config file.\n");
-	printf("\nSee http://mosquitto.org/ for more information.\n\n");
+	printf("\nSee https://mosquitto.org/ for more information.\n\n");
 }
 
 int config__parse_args(struct mosquitto_db *db, struct mosquitto__config *config, int argc, char *argv[])