Include examples in CI tests

Also fix and update examples and documentation where required
This allows to make sure examples are actually runnable avoiding them to
become outdated

test/bench_30_classes_30_methods_9_args.cpp

@@ -1071,3 +1071,8 @@ namespace
     mock_class_29 c_29;
     mock_class_30 c_30;
 }
+
+int main()
+{
+    return 0;
+}