doc: adding example for implementations without traits
sys: reveal std::io representation to sys module

This commit adds a `AsInner` trait to `sys_common` and provides
implementations on many `std::io` types. This is a building block for
exposing platform-specific APIs that hook into `std::io` types.
libs: add std::os::unix module

The new `std::os::unix` module exposes several extension traits
for extracting file descriptors from `std::io` types.
libs: add std::os::windows module

The new `std::os::windows` module exposes several extension traits
for extracting file descriptors, sockets, and handles from `std::io`
types.
Search for implemented kinds recursively on Trait types. Fixes #15155 and #13155.
add MoveItems to RingBuf, fixes #19085
Rename unwrap functions to into_inner

This change applies the conventions to unwrap listed in [RFC 430][rfc] to rename
non-failing `unwrap` methods to `into_inner`. This is a breaking change, but all
`unwrap` methods are retained as `#[deprecated]` for the near future. To update
code rename `unwrap` method calls to `into_inner`.

[rfc]: https://github.com/rust-lang/rfcs/pull/430
[breaking-change]

Closes #13159
cc #19091
compiletest: extend syntax with support for choosing same line as previous line.
Add `node_to_user_string`, `node_to_string` variant that drops id from output.
rustdoc: Render associated types on traits and impls
rustdoc: render ast::QPath

Fix #18594
Fixed "::::" appearing in module_path!()
Added test for module_path! fix
rustdoc: Render Sized? on traits and generics

Both `trait Foo for Sized?` and `<Sized? T>` are handled correctly.

Fix #18515
Merge libsync into libstd

This patch merges the `libsync` crate into `libstd`, undoing part of the
facade. This is in preparation for ultimately merging `librustrt`, as
well as the upcoming rewrite of `sync`.

Because this removes the `libsync` crate, it is a:

[breaking-change]

However, all uses of `libsync` should be able to reroute through
`std::sync` and `std::comm` instead.
remove the generation of grammar from the reference
Clean up FileType enum following enum namespacing

All of the enum components had a redundant 'Type' specifier: TypeSymlink, TypeDirectory, TypeFile. This change removes them, replacing them with a namespace: FileType::Symlink, FileType::Directory, and FileType::RegularFile.

RegularFile is used instead of just File, as File by itself could be mistakenly thought of as referring to the struct.

[breaking-change]
std: Export BinarySearchResult

At the same time remove the `pub use` of the variants in favor of accessing
through the enum type itself. This is a breaking change as the `Found` and
`NotFound` variants must now be imported through `BinarySearchResult` instead of
just `std::slice`.

[breaking-change]
Closes #19272
Add methods to go from a slice iterators to a slice.

A slice iterator is isomorphic to a slice, just with a slightly
different form: storing start and end pointers rather than start pointer
and length. This patch reflects this by making converting between them
as easy as `iter.as_slice()` (or even `iter[]` if the shorter lifetime
is ok). That is, `slice.iter().as_slice() == slice`.
auto merge of #18966 : huonw/rust/iter2slice, r=aturon

A slice iterator is isomorphic to a slice, just with a slightly
different form: storing start and end pointers rather than start pointer
and length. This patch reflects this by making converting between them
as easy as `iter.as_slice()` (or even `iter[]` if the shorter lifetime
is ok). That is, `slice.iter().as_slice() == slice`.

r? @aturon