Updated Submodule to current Harfbuzz head.

[asibahi]

1. Updated submodule
2. A couple of clippy fixes
3. ran bindgen on hb.h . There doesn't seem to be any changes aside from platforms and version numbers.

Mind you that I did not update the rust code. Many functions are only in the bindings and have not been encapsulated in rust land.

(Should close this? #41)

[behdad]

Thanks. Yeah I think most of the work recently has been in the subset land. And at any rate, I don't expect this crate fully binds all HB API?

[asibahi]

I used the hb.h file for bindgen. So any functions exposed there should be exposed as unsafe functions in Rust. All that's missing is encapsulation.