Several broken links in backend/internal documentation

[isislovecruft]

#283 fixes a few of them but I think there's more since the repo restructuring last year. I don't have access to the buckets hosting the http://doc-internal.dalek.rs pages, so I'm not able to update them.

[pinkforest]

Parallel doc

README.md:[parallel_doc]: https://doc-internal.dalek.rs/curve25519_dalek/backend/vector/avx2/index.html
src/lib.rs://! [parallel_doc]: https://doc-internal.dalek.rs/curve25519_dalek/backend/vector/avx2/index.html

Questions / Findings

1. This is hard-coded to doc-internal.dalek.rs - not relative link
2. dalek.rs is just doing make doc and make doc-internal using nightly toolchain I'm assuming ?
3. Should this continue to rely on dalek.rs or should it moved to docs.rs generated as other crates ?

make doc issue

[target/doc/curve25519_dalek/]backend/vector documentation doesn't get generated -

If continuing to use this method to generate docs is preferred -

Problem is some documentation is behind some unstable feature flags

Which would need to be in RUSTDOCFLAGS which does not honor RUSTFLAGS which I didn't see set either

I can get the backend/vector to generate:

RUSTDOCFLAGS="-C target_feature=+avx2" cargo rustdoc --features "nightly std simd_backend" -- --html-in-header docs/assets/rustdoc-include-katex-header.html --document-private-items

Also I noticed that there are `#[cfg(rustdoc)] in places but this isn't used anymore

This probably should move to doc_cfg pattern

#![feature(doc_cfg)]
#[doc(cfg(feature = "xx"))]

docs.rs ?

Should the docs move to docs.rs ? For this would have to setup docsrs e.g.

[package.metadata.docs.rs]
# document all features
all-features = true
# defines the configuration attribute `docsrs`
rustdoc-args = ["--cfg", "docsrs"]

[pinkforest]

Fixed in #439

Validating all the links with lychee

[pinkforest]

This was fixed via #439 @rozbb