Rustdoc: glob reexport may duplicate module

[WaffleLapkin]

If glob reexport reexports module x and there is already module x, the documentation duplicates.

pub mod sub {
    pub struct Item;

    pub mod prelude {
        pub use super::Item;
    }    
}

pub mod prelude {}

#[doc(inline)]
pub use sub::*;

Current behaviour:

(prelude module is duplicated, though both prelude module links point to crate::prelude as expected)

The expected behaviour: prelude module is only shown once.

[longfangsong]

@rustbot claim

[aliemjay]

@rustbot claim