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

extras/tests/FailingBuilds/CMakeLists.txt

@@ -31,11 +31,9 @@ add_executable(Issue1189 Issue1189.cpp)
 build_should_fail(Issue1189)
 
 add_executable(read_long_long read_long_long.cpp)
-set_property(TARGET read_long_long PROPERTY CXX_STANDARD 11)
 build_should_fail(read_long_long)
 
 add_executable(write_long_long write_long_long.cpp)
-set_property(TARGET write_long_long PROPERTY CXX_STANDARD 11)
 build_should_fail(write_long_long)
 
 add_executable(delete_jsondocument delete_jsondocument.cpp)

extras/tests/FailingBuilds/read_long_long.cpp

@@ -9,10 +9,6 @@
 #  error This test requires sizeof(long) < 8
 #endif
 
-#if !ARDUINOJSON_HAS_LONG_LONG
-#  error This test requires C++11
-#endif
-
 ARDUINOJSON_ASSERT_INTEGER_TYPE_IS_SUPPORTED(long long)
 int main() {
   DynamicJsonDocument doc(1024);