Highlight Rust code fenced in code blocks inside comments
Highlight Rust code fenced in code blocks inside comments

As requested in #63.

This means that stuff like the following get highlighted:

//! ```
//! use std::thread;
//! use std::sync::mpsc::channel;
//! ```

The color for `//!` is still matching the one of comments, but the
fenced code is highlighted.

Currently only `//!` and `///` comments are supported, and Rust
is assumed.

rust-lang/rust.vim