rustdoc: Fix some more broken links
rustdoc: Filter private methods from inlined impls

Closes #14583
mk: Less noisy rustdoc invocations
rustdoc: Ensure external impls are inlined once

If the type associated with the impl is `pub use`'d or referenced twice in a
downstream crate, the impl will attempt to be inlined twice.

Closes #14584
rustdoc: Deduplicate lists of implementors

Inlining caused implementors to show up multiple times.

cc #14584
rustdoc: Correctly inline required/provided methods

Apparently relying on provided_source in ty::Method is unreliable!

Closes #14594
Adding show impl for Rc
std: add `IterReader` to adapt iterators into readers
Add next_permutation and prev_permutation onto MutableOrdVector<T>.

Unlike ImmutableClonableVector::permutations() which returns an iterator,
cloning the entire array each iteration, these methods mutate the vector in-place.
For that reason, these methods are much faster; between 35-55 times faster,
depending on the benchmark. They also generate permutations in lexicographical order.
std: Remove generics from Option::expect

This commit removes the <M: Any + Send> type parameter from Option::expect in
favor of just taking a hard-coded `&str` argument. This allows this function to
move into libcore.

Previous code using strings with `expect` will continue to work, but code using
this implicitly to transmit task failure will need to unwrap manually with a
`match` statement.

[breaking-change]
Closes #14008
rustdoc: Put primitives in respective modules

The logical location for the documentation of a primitive is in the module that
declared it was a module for that primitive.
Fixes #13843.

An empty regex is a valid regex that always matches. This behavior
is consistent with at least Go and Python.

A couple regression tests are included.
Some minor documentation touchups for libregex. Fixes #13800.
syntax: shuffle some allocation out of binop_to_str
Add comments for the token table
auto merge of #14634 : BurntSushi/rust/fix-13843, r=alexcrichton

An empty regex is a valid regex that always matches. This behavior
is consistent with at least Go and Python.

A couple regression tests are included.

I'd just assume that an empty regex is an invalid regex and that an error should be returned (I can't think of any reason to use an empty regex?), but it's probably better to be consistent with other regex libraries.
auto merge of #14635 : BurntSushi/rust/regex-doco-touchups, r=alexcrichton
libc: only provide an rlib.

There's absolutely no reason for `libc` to be offered as a dynamic
library.
Add code example to std::os::getenv for unix.
Implement Show for RingBuf