Support default __stdcall calling convention on tests as well

tests/parse_hex4.c

@@ -64,7 +64,7 @@ static void parse_hex4_should_parse_mixed_case(void)
     TEST_ASSERT_EQUAL_INT(0xBEEF, parse_hex4((const unsigned char*)"BEEF"));
 }
 
-int main(void)
+int CJSON_CDECL main(void)
 {
     UNITY_BEGIN();
     RUN_TEST(parse_hex4_should_parse_all_combinations);