message: clippy: fix inline_always warnings
diff: #![doc(html_logo_url = "http://fulmicoton.com/tantivy-logo/tantivy-logo.png")]
  #![allow(unknown_lints)] // for the clippy lint options
  #![allow(module_inception)]
  +#![cfg_attr(feature = "cargo-clippy", allow(inline_always))]
  #![feature(box_syntax)]
  #![feature(optin_builtin_traits)]
  