Documentation fixes suggested by catalyst.

/// # Note

///

/// An unfortunate limitation of the rustc compiler (as of 1.25.0-nightly), is

/// that the above code compiles, however if we were to change the assignment of

/// `tuesday` as follows, it will fail to compile, because Rust macros are

/// expanded at parse time, and at parse time there is no symbols table

/// available.

/// that the first example above compiles, but if we were to change the

/// assignment of `tuesday` as follows, it will fail to compile, because Rust

/// macros are expanded at parse time, and at parse time there is no symbol

/// table available.

///

/// ```ignore

/// tuesday = cstr!(message);