Function gstreamer_sys::gst_meta_register_custom

pub unsafe extern "C" fn gst_meta_register_custom(
    name: *const c_char, 
    tags: *mut *const c_char, 
    transform_func: GstCustomMetaTransformFunction, 
    user_data: gpointer, 
    destroy_data: GDestroyNotify
) -> *const GstMetaInfo

This is supported on crate feature v1_20 only.