- Remove dead link to `rustc_attr` crate.
- Add link to `rustc_attr_parsing` crate.
- Split up first paragraph so it looks better at crate-level summary
Adds `#[rustc_force_inline]` which is similar to always inlining but
reports an error if the inlining was not possible, and which always
attempts to inline annotated items, regardless of optimisation levels.
It can only be applied to free functions to guarantee that the MIR
inliner will be able to resolve calls.
