Log Message:
rust: Update to version 1.28.0.

NetBSD/i386 is temporarily disabled due to missing binary bootstraps.

Version 1.28.0 (2018-08-02)
===========================

Language
--------
- [The `#[repr(transparent)]` attribute is now stable.][51562] This attribute
  allows a Rust newtype wrapper (`struct NewType<T>(T);`) to be represented as
  the inner type across Foreign Function Interface (FFI) boundaries.
- [The keywords `pure`, `sizeof`, `alignof`, and `offsetof` have been unreserved
  and can now be used as identifiers.][51196]
- [The `GlobalAlloc` trait and `#[global_allocator]` attribute are now
  stable.][51241] This will allow users to specify a global allocator for
  their program.
- [Unit test functions marked with the `#[test]` attribute can now return
  `Result<(), E: Debug>` in addition to `()`.][51298]
- [The `lifetime` specifier for `macro_rules!` is now stable.][50385] This
  allows macros to easily target lifetimes.

Compiler
--------
- [The `s` and `z` optimisation levels are now stable.][50265] These optimisations
  prioritise making smaller binary sizes. `z` is the same as `s` with the
  exception that it does not vectorise loops, which typically results in an even
  smaller binary.
- [The short error format is now stable.][49546] Specified with
  `--error-format=short` this option will provide a more compressed output of
  rust error messages.
- [Added a lint warning when you have duplicated `macro_export`s.][50143]
- [Reduced the number of allocations in the macro parser.][50855] This can
  improve compile times of macro heavy crates on average by 5%.

Libraries
---------
- [Implemented `Default` for `&mut str`.][51306]
- [Implemented `From<bool>` for all integer and unsigned number types.][50554]
- [Implemented `Extend` for `()`.][50234]
- [The `Debug` implementation of `time::Duration` should now be more easily
  human readable.][50364] Previously a `Duration` of one second would printed as
  `Duration { secs: 1, nanos: 0 }` and will now be printed as `1s`.
- [Implemented `From<&String>` for `Cow<str>`, \ 
`From<&Vec<T>>` for `Cow<[T]>`,
  `From<Cow<CStr>>` for `CString`, `From<CString>, \ 
From<CStr>, From<&CString>`
  for `Cow<CStr>`, `From<OsString>, From<OsStr>, \ 
From<&OsString>` for
  `Cow<OsStr>`, `From<&PathBuf>` for `Cow<Path>`, and \ 
`From<Cow<Path>>`
  for `PathBuf`.][50170]
- [Implemented `Shl` and `Shr` for `Wrapping<u128>`
  and `Wrapping<i128>`.][50465]
- [`DirEntry::metadata` now uses `fstatat` instead of `lstat` when
  possible.][51050] This can provide up to a 40% speed increase.
- [Improved error messages when using `format!`.][50610]

Stabilized APIs
---------------
- [`Iterator::step_by`]
- [`Path::ancestors`]
- [`SystemTime::UNIX_EPOCH`]
- [`alloc::GlobalAlloc`]
- [`alloc::Layout`]
- [`alloc::LayoutErr`]
- [`alloc::System`]
- [`alloc::alloc`]
- [`alloc::alloc_zeroed`]
- [`alloc::dealloc`]
- [`alloc::realloc`]
- [`alloc::handle_alloc_error`]
- [`btree_map::Entry::or_default`]
- [`fmt::Alignment`]
- [`hash_map::Entry::or_default`]
- [`iter::repeat_with`]
- [`num::NonZeroUsize`]
- [`num::NonZeroU128`]
- [`num::NonZeroU16`]
- [`num::NonZeroU32`]
- [`num::NonZeroU64`]
- [`num::NonZeroU8`]
- [`ops::RangeBounds`]
- [`slice::SliceIndex`]
- [`slice::from_mut`]
- [`slice::from_ref`]
- [`{Any + Send + Sync}::downcast_mut`]
- [`{Any + Send + Sync}::downcast_ref`]
- [`{Any + Send + Sync}::is`]

Cargo
-----
- [Cargo will now no longer allow you to publish crates with build scripts that
  modify the `src` directory.][cargo/5584] The `src` directory in a crate should be
  considered to be immutable.

Misc
----
- [The `suggestion_applicability` field in `rustc`'s json output is now
  stable.][50486] This will allow dev tools to check whether a code suggestion
  would apply to them.

Compatibility Notes
-------------------
- [Rust will no longer consider trait objects with duplicated constraints to
  have implementations.][51276] For example the below code will now fail
  to compile.
  ```rust
  trait Trait {}

  impl Trait + Send {
      fn test(&self) { println!("one"); } //~ ERROR duplicate \ 
definitions with name `test`
  }

  impl Trait + Send + Send {
      fn test(&self) { println!("two"); }
  }
  ```