Advisories for Cargo/Mopa package

The mopa crate redefines the deprecated TraitObject struct from core::raw like so:

The mopa crate redefines the deprecated TraitObject struct from core::raw. This is done to then transmute a reference to a trait object (&dyn Trait for any trait Trait) into this struct and retrieve the data field for the purpose of downcasting. This is used to implement downcast_ref_unchecked(), in terms of which downcast_ref() is also implemented. Same goes for mutable reference downcasting and Box downcasting. The Rust compiler explicitly reserves the …