Fix dyn and import warnings

[GuillaumeGomez]

cc @EPashkin @sdroege

[EPashkin]

Thanks and 👍
Note: cairo also have one warning

warning: trait objects without an explicit `dyn` are deprecated
  --> D:/eap/rust/0/cairo\src\error.rs:73:32
   |
73 |     fn cause(&self) -> Option<&Error> {
   |                                ^^^^^ help: use `dyn`: `dyn Error`

[sdroege]

👍

[GuillaumeGomez]

@EPashkin One crate at a time! Currently facing gio. :)