Add const

 https://randomascii.wordpress.com/2017/01/08/add-a-const-here-delete-a-const-there/

src/civetweb.c

@@ -2362,7 +2362,7 @@ enum {
 /* Config option name, config types, default value.
  * Must be in the same order as the enum const above.
  */
-static struct mg_option config_options[] = {
+static const struct mg_option config_options[] = {
 
     /* Once for each server */
     {"listening_ports", MG_CONFIG_TYPE_STRING_LIST, "8080"},