Allowing HEAD method for CGI requests

mongoose.c

@@ -4243,6 +4243,7 @@ static void handle_request(struct mg_connection *conn) {
                           strlen(conn->ctx->config[CGI_EXTENSIONS]),
                           path) > 0) {
     if (strcmp(ri->request_method, "POST") &&
+        strcmp(ri->request_method, "HEAD") &&
         strcmp(ri->request_method, "GET")) {
       send_http_error(conn, 501, "Not Implemented",
                       "Method %s is not implemented", ri->request_method);