std: add `IterReader` to adapt iterators into readers
Add code example to std::os::getenv for unix.
Implement Show for RingBuf
Mark the exit of infinite loops as unreachable
Fix an ICE when a function argument is of the bottom type

Fixes #13352
collections: optimize `HashMap`. Add `DefaultResizePolicy`.

Refactored the load factor and the minimum capacity out of HashMap.
The size of HashMap<K, V> is now 64 bytes by default on a 64-bit platform
(or 48 bytes, that is 2 words less, with FNV)
Added a documentation in a few places to clarify the behavior.
std: Improve non-task-based usage

A few notable improvements were implemented to cut down on the number of aborts
triggered by the standard library when a local task is not found.

* Primarily, the unwinding functionality was restructured to support an unsafe
  top-level function, `try`. This function invokes a closure, capturing any
  failure which occurs inside of it. The purpose of this function is to be as
  lightweight of a "try block" as possible for rust, intended for use when the
  runtime is difficult to set up.

  This function is *not* meant to be used by normal rust code, nor should it be
  consider for use with normal rust code.

* When invoking spawn(), a `fail!()` is triggered rather than an abort.

* When invoking LocalIo::borrow(), which is transitively called by all I/O
  constructors, None is returned rather than aborting to indicate that there is
  no local I/O implementation.

* Invoking get() on a TLD key will return None if no task is available

* Invoking replace() on a TLD key will fail if no task is available.

A test case was also added showing the variety of things that you can do without
a runtime or task set up now. In general, this is just a refactoring to abort
less quickly in the standard library when a local task is not found.
Fixes #14185.

This fix suppresses dead_code warnings from code generated by regex! when
the result of regex! is unused. Correct behavior should be a single
unused variable warning.

Regression tests are included for both `let` and `static` bound regex!
values.
travis: Prevent timeouts with travis_wait

The most frequent failure for our travis builds is running into the timeout
limits when building the compiler itself. Building librustc takes a very long
amount of time, often hitting the 10 minutes with no output threshold that
travis imposes on us.

This commit switches the relevant `make` step to being wrapped in the
`travis_wait` command [1]. This command will print something once a minute so as
to not time out a build.

This will hopefully enable us to have fewer flaky builds on travis!

[1]: http://docs.travis-ci.com/user/build-timeouts/
Fixed weird grammar in lifetimes guide.
auto merge of #14568 : erickt/rust/slice-update, r=alexcrichton

This PR adds two features to make it possible to transform an `Iterator<u8>` into a `Reader`. The first patch adds a method to mutable slices that allows it to be updated with an `Iterator<T>` without paying for the bounds cost. The second adds a Iterator adaptor, `IterReader`, to provide that `Reader` interface.

I had two questions. First, are these named the right things? Second, should `IterReader` instead wrap an `Iterator<Result<u8, E>>`? This would allow you to `IterReader::new(rdr.bytes())`, which could be useful if you want to apply some iterator transformations on a reader while still exporting the Reader interface, but I'd expect there'd be a lot of overhead annotating each byte with an error result.
relicense shootout-meteor.rs

part of #14248, fix #14420

Removed @richo's contribution (outdated comment)

Quoting @brson: let's move forward with this one. The only
statement I'm missing is @richo's and it sounds like his was a
minor patch.
rustdoc: Include supertraits on inlined traits

Previously, documentation for an inlined trait (i.e. a trait imported
and reexported from another crate) didn't display the trait's
supertraits.

Closes #14636
Update AUTHORS.txt
Adding examples and possible failures for getcwd.

For both window and unix platforms.
auto merge of #14640 : tomjakubowski/rust/fix-14636, r=huonw

Previously, documentation for an inlined trait (i.e. a trait imported
and reexported from another crate) didn't display the trait's supertraits.

Closes #14636
auto merge of #14642 : aochagavia/rust/pr, r=alexcrichton

The contents of a `RingBuf` are shown in the same way as the contents of a `Vector`. See the tests for examples.
Remove a warning  (./configure: 1140: [: unexpected operator) when built with --disable-manage-submodules
auto merge of #14643 : jakub-/rust/infinite-loop-unreachable, r=alexcrichton
auto merge of #14644 : alexcrichton/rust/more-no-runtime-use-cases, r=brson

A few notable improvements were implemented to cut down on the number of aborts
triggered by the standard library when a local task is not found.

* Primarily, the unwinding functionality was restructured to support an unsafe
  top-level function, `try`. This function invokes a closure, capturing any
  failure which occurs inside of it. The purpose of this function is to be as
  lightweight of a "try block" as possible for rust, intended for use when the
  runtime is difficult to set up.

  This function is *not* meant to be used by normal rust code, nor should it be
  consider for use with normal rust code.

* When invoking spawn(), a `fail!()` is triggered rather than an abort.

* When invoking LocalIo::borrow(), which is transitively called by all I/O
  constructors, None is returned rather than aborting to indicate that there is
  no local I/O implementation.

A test case was also added showing the variety of things that you can do without
a runtime or task set up now. In general, this is just a refactoring to abort
less quickly in the standard library when a local task is not found.