Pass through #[doc(hidden)] attribute

[mattiekat]

Since cxx is so awesome at wrapping C++, it is nice to be able to export the interface directly on the rust side, but sometimes it is preferable to hide certain functions that are used directly by a custom impl MyCxxType. Since all functions are public they all by default want to show up in the docs which I find myself using a lot given proc macro support in IDEs is still early.

[dtolnay]

Good call — I've published 1.0.56 with support for doc(hidden).

[mattiekat]

Hmm, testing 1.0.56 and I am seeing

#[doc(hidden)]
     ^ expected `=`

Example code (that is an approximation of what I have):

#[cxx::bridge(namespace = "some::ns")]
pub mod ffi {

    unsafe extern "C++" {
        type ExternType;

        #[doc(hidden)]
        #[cxx_name = "doThing"]
        fn _do_thing() -> ExternType;
    }        
}