the use of lazily evaluated alternatives when appropriate. These
comments are intended to echo a clippy lint on the same topic (see
https://rust-lang-nursery.github.io/rust-clippy/master/index.html#or_fun_call)

It appears to be a simple oversight that `result::IntoIter<T>` doesn't
implement `Clone` (where `T: Clone`).  We do already have `Clone` for
`result::Iter`, as well as the similar `option::IntoIter` and `Iter`.

The easy parts of RFC 1859.  (Just the trait and the lowering, none of
the error message improvements nor the insta-stable impl for Option.)

This commit applies the stabilization/deprecations of the 1.16.0 release, as
tracked by the rust-lang/rust issue tracker and the final-comment-period tag.

The following APIs were stabilized:

* `VecDeque::truncate`
* `VecDeque::resize`
* `String::insert_str`
* `Duration::checked_{add,sub,div,mul}`
* `str::replacen`
* `SocketAddr::is_ipv{4,6}`
* `IpAddr::is_ipv{4,6}`
* `str::repeat`
* `Vec::dedup_by`
* `Vec::dedup_by_key`
* `Result::unwrap_or_default`
* `<*const T>::wrapping_offset`
* `<*mut T>::wrapping_offset`
* `CommandExt::creation_flags` (on Windows)
* `File::set_permissions`
* `String::split_off`

The following APIs were deprecated

* `EnumSet` - replaced with other ecosystem abstractions, long since unstable

Closes #27788
Closes #35553
Closes #35774
Closes #36436
Closes #36949
Closes #37079
Closes #37087
Closes #37516
Closes #37827
Closes #37916
Closes #37966
Closes #38080

Most of the Rust community agrees that the vec! macro is clearer when
called using square brackets [] instead of regular brackets (). Most of
these ocurrences are from before macros allowed using different types of
brackets.

There is one left unchanged in a pretty-print test, as the pretty
printer still wants it to have regular brackets.

This trait can be used to avoid the overhead of a fuse wrapper when an iterator
is already well-behaved.

Conforming to: RFC 1581
Closes: #35602

This change improves the code example for try!,
avoiding to use try! in the example code that shows
what code constructs try! can replace.

Fixes #9447

Move functions out of their impl blocks; avoids unnecessary
monomorphization by type parameters that are irrelevant to the message
output.

Option::expect, Result::unwrap, unwrap_err, expect

These methods are marked inline, but insert a big chunk of formatting
code, as well as other error path related code, such as deallocating
a std::io::Error if you have one.

We can explicitly separate out that code path into a function that is
never inline, since the panicking case should always be rare.

This is a standard "clean out libstd" commit which removes all 1.5-and-before
deprecated functionality as it's now all been deprecated for at least one entire
cycle.