rustdoc: Resolve `&str` as `str`
People almost always are referring to `&str`, not `str`, so this will
save a manual link resolve in many cases.
Note that we already accept `&` (resolves to `reference`) in intra-doc
links, so this shouldn't cause breakage.
r? `@jyn514`
It's not valid Rust code and it can easily be confused with a wildcard
glob pattern or something else. People can always use `pointer` instead,
so it's just removing an alias.
It hasn't hit stable yet (I think it's still on nightly), so it's okay
to remove it. (We can always add it back later if we change our mind
too.)
People almost always are referring to `&str`, not `str`, so this will
save a manual link resolve in many cases.
Note that we already accept `&` (resolves to `reference`) in intra-doc
links, so this shouldn't cause breakage.
This does *not* currently work for associated items that are
auto-implemented by the compiler (e.g. `never::eq`), because they aren't
present in the source code. I plan to fix this in a follow-up PR.
