Support multiple fields: deref_target attribute

[Ploppz]

trafficstars

Use deref_target when there is more than one field to chose from (excluding any PhantomData, as before).

#[derive(Deref)]
struct StringWrapper {
    additional_data: i32,
    more_data: i32,
    #[deref_target]
    inner: String,
};

And update all dependencies to latest.

[Ploppz]

I think I addressed all your concerns. What do you think now?

[azriel91]

@sgrif @Eijebong would one of you have time to take a look at this? Thank you

[Ten0]

This is great! I often could use this!

[azriel91]

@sgrif @Eijebong would one of you have time to take a look at this? Thank you

[Ten0]

Any chance this could get merged?

(Btw this conflicts)

[Ploppz]

Fixed the conflicts by rebasing.