make main() return something

tests/testPrograms/URLtest.cpp

@@ -47,4 +47,5 @@ int main(void) {
     test_parser("http://www.example.org:9090/this/path?query",                    "http", "", "www.example.org", 9090, "/this/path", "query", "");
     test_parser("http://www.example.org/this/path?query",                         "http", "", "www.example.org", 80, "/this/path", "query", "");
     test_parser("http://www.example.org?query",                                   "http", "", "www.example.org", 80, "/", "query", "");
+    return 0;
 }