Rust lexer chokes on `#idents` inside `quote!` macro

(Original issue 1357 created by None on 2017-06-18T14:22:25.731309+00:00)

Inside `quote!( ... )` or `quote!{ ... }`, identifiers following an octothorpe (e.g. `#my_var`) should be highlighted.

Instead, it currently errors.

Examples:

```rust
let foo = "bar";
let bar = quote!(#foo);

Ok(quote! {
    let foo = #foo;
})
```