The signal could be named changed.

We just have to add it in ugly/sixtyfps_widgets.60
and also in NativeSlider in builtins.60 and widgets.rs

When integrating connxr in C++ we have to disable the C++ function mangling, so our c functions can be linked correctly.
We would need to put all our prototypes or the complete header inside sth like

#ifdef __cplusplus
extern "C" {
#endif

...

#ifdef __cplusplus
}
#endif