Include license notice in generated headers

[afonso360]

Hi, some licenses such as the GPLv2 require a notice in the headers produced, this is just a simple operation of prepending a comment to the generated headers, would you please be able to add this feature to your library?

This is more of a convinience feature as I can just as well open each header file and prepend the license text myself. (Which is what im currently doing)

If this is more appropriate for the rusty-binder crate tell me and ill open an issue there.

[kinetiknz]

You can use Cheddar::insert_code to insert the license text, for example see https://github.com/mozilla/mp4parse-rust/blob/master/mp4parse_capi/build.rs. The only (slight) down side is that it's inserted after the two C99 headers.