bump stdsimd; make intra_doc_link_resolution_failure an error again; make lints more consistent
I made `intra_doc_link_resolution_failure` warn so that it would properly respect `deny-warnings = false` in `config.toml`. `#[warn]` still become errors with `-D warnings` so I thought this was fine.
Turns out however that we don't pass `-D warnings` when running rustdoc, so for additional rustdoc-lints we need to set them to `deny`.
Also sue the opportunity to make the lint flags more consistent between libcore, liballoc, libstd.
Cc @gnzlbg for the *big* stdsimd update.
c712d38634