Generator docs: add note about clang documentation string options
I believe this should fix
@@ -719,6 +719,14 @@ impl Builder {
/// implement some processing on comments to work around issues as described
/// in [rust-bindgen issue
/// #426](https://github.com/rust-lang/rust-bindgen/issues/426).
+ ///
+ /// Note that clang by default excludes comments from system headers, pass
+ /// `-fretain-comments-from-system-headers` as
+ /// [`clang_arg`][Builder::clang_arg] to include them. It can also be told
+ /// to process all comments (not just documentation ones) using the
+ /// `-fparse-all-comments` flag. See [slides on clang comment parsing](
+ /// https://llvm.org/devmtg/2012-11/Gribenko_CommentParsing.pdf) for
+ /// background and examples.
pub fn generate_comments(mut self, doit: bool) -> Self {
self.options.generate_comments = doit;
self
