This way, the crates can be published without interfering with
potential future non-bindings `nix-` crates, if Nix proper wants to
have native rust code, for instance.
See README. Most of this is in accordance with the bindgen introduction.
The c_headers function was taken from Zach Mitchell's work on bindings.
Co-authored-by: Zach Mitchell <zmitchell@fastmail.com>
(cherry picked from commit 83d8ae6b26d341bbd452a77d7361f58c06a2d322)
