Run all tests with C++11 enabled (#1820)

extras/tests/MixedConfiguration/use_long_long_0.cpp

@@ -0,0 +1,16 @@
+#define ARDUINOJSON_USE_LONG_LONG 0
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("ARDUINOJSON_USE_LONG_LONG == 0") {
+  DynamicJsonDocument doc(4096);
+
+  doc["A"] = 42;
+  doc["B"] = 84;
+
+  std::string json;
+  serializeJson(doc, json);
+
+  REQUIRE(json == "{\"A\":42,\"B\":84}");
+}