Enabled comments in bindgen and added doxygen pre-processor

[nikarh]

Motivation

• Rustdoc comments integrate well with IDEs and improve dev experience
• Using docs.rs is a very convenient way to understand what things do and how things work

Implementation

Luckily, comments in the headers mostly follow Doxygen formatting. doxygen-rs crate does exactly what we need and converts them to rustdoc format.

Without additional pre-processing, doxygen_rs::transform panics due to some mistakes and unexpected things in the comments, thus the callback first fixes them.
After the transformation, some of the prefixes used for field comments in headers are stripped away, e.g. this

I've also committed the generated bindings, although I'm not sure what our workflow is with them (as in should they be updated solely by gh actions, or is committing them ok?). Anyway, the committed bindings show how the comments look like with these changes.

[pheki]

Great work!

I've also committed the generated bindings, although I'm not sure what our workflow is with them (as in should they be updated solely by gh actions, or is committing them ok?). Anyway, the committed bindings show how the comments look like with these changes.

Yep, you should commit them, CI will check if they're correct. For now CI only commits generated bindings when creating or updating the "Update bindings" PR.

Can you add a new version to the changelog? Something like

## [0.3.4] - Unreleased

### Added

- Doc comments are now also copied from vitasdk (#30).

[nikarh]

I made a PR to doxygen-rs to enable code blocks that will retain the formatting - Techie-Pi/doxygen-rs/pull/9.

[pheki]

It seems that your last commit adds comments for deprecated fields, such as:

+ #[doc = "Others read permission. Deprecated, use ::SCE_S_IXSYS"]
  pub const SCE_S_IROTH: SceIoAccessMode = 4;

And those are good, but they're not getting generated on my end... Do you know why?