Write comments and docstrings to the header file.

[Sean1708]

Comments are a common form of documentation in header files so any rust docstrings should be written to the header file.

Should rust comments be written to the header file too?

[Sean1708]

Mostly done, just need to indent them correctly now.

[Sean1708]

My suggestion would be to have a function signature of

fn retrieve_docstring(attr: &Attribute, prepend: &str) -> String {

and call it with a closure

let (_, docs) = parse_attr(&var.node.attrs, |_| true, |attr| retrieve_docstring(attr, "\t"));