Update RELEASES.md for 1.55.0

Co-authored-by: Eric Huss <eric@huss.org>
Co-authored-by: inquisitivecrystal <22333129+inquisitivecrystal@users.noreply.github.com>
Co-authored-by: Mark Rousskov <mark.simulacrum@gmail.com>
Co-authored-by: Daniel Giger <danielg3432@gmail.com>

RELEASES.md

@@ -1,3 +1,145 @@
+Version 1.55.0 (2021-09-09)
+============================
+
+Language
+--------
+- [You can now write open "from" range patterns (`X..`), which will start at `X` and
+  will end at the maximum value of the integer.][83918]
+- [You can now explicitly import the prelude of different editions
+  through `std::prelude` (e.g. `use std::prelude::rust_2021::*;`).][86294]
+
+Compiler
+--------
+- [Added tier 3\* support for `powerpc-unknown-freebsd`.][87370]
+- [Added tier 3 support for `powerpc64le-unknown-freebsd`.][83572]
+
+\* Refer to Rust's [platform support page][platform-support-doc] for more
+   information on Rust's tiered platform support.
+
+Libraries
+---------
+
+- [Updated std's float parsing to use the Eisel-Lemire algorithm.][86761]
+  These improvements should in general provide faster string parsing of floats,
+  no longer reject certain valid floating point values, and reduce
+  the produced code size for non-stripped artifacts.
+- [`string::Drain` now implements `AsRef<str>` and `AsRef<[u8]>`.][86858]
+- [`collections::{BinaryHeap, BTreeSet, HashSet, LinkedList, VecDeque}` now
+  implement `From<[T; N]>`.][84111]
+- [`collections::{BTreeMap, HashMap}` now implement `From<[(K, V); N]>`.][84111]
+  This allows you to write the following;
+  ```rust
+  let highscores = std::collections::HashMap::from([
+      ("Alice", 9000u32),
+      ("Bob", 7250),
+      ("Charlie", 5500),
+  ]);
+  ```
+
+Stabilised APIs
+---------------
+
+- [`Bound::cloned`]
+- [`Drain::as_str`]
+- [`IntoInnerError::into_error`]
+- [`IntoInnerError::into_parts`]
+- [`MaybeUninit::assume_init_mut`]
+- [`MaybeUninit::assume_init_ref`]
+- [`MaybeUninit::write`]
+- [`array::map`]
+- [`ops::ControlFlow`]
+- [`x86::_bittest`]
+- [`x86::_bittestandcomplement`]
+- [`x86::_bittestandreset`]
+- [`x86::_bittestandset`]
+- [`x86_64::_bittest64`]
+- [`x86_64::_bittestandcomplement64`]
+- [`x86_64::_bittestandreset64`]
+- [`x86_64::_bittestandset64`]
+
+The following previously stable functions are now `const`.
+
+- [`str::from_utf8_unchecked`]
+- [`mem::transmute`]
+
+
+Cargo
+-----
+- [Cargo will now deduplicate compiler diagnostics to the terminal when invoking
+  rustc in parallel such as when using `cargo test`.][cargo/9675]
+- [The package definition in `cargo metadata` now includes the `"default_run"`
+  field from the manifest.][cargo/9550]
+- [Added `cargo d` as an alias for `cargo doc`.][cargo/9680]
+
+Rustdoc
+-------
+- [Added "Go to item on exact match" search option.][85876]
+- [The "Implementors" section on traits no longer shows redundant
+  method definitions.][85970]
+- [Trait implementations are toggled open by default.][86260] This should make the
+  implementations more searchable by tools like `CTRL+F` in your browser.
+- [Intra-doc links should now correctly resolve associated items (e.g. methods)
+  through type aliases.][86334]
+- [Traits which are marked with `#[doc(hidden)]` will no longer appear in the
+  "Trait Implementations" section.][86513]
+
+
+Compatibility Notes
+-------------------
+- [std functions that return an `io::Error` will no longer use the
+  `ErrorKind::Other` variant.][85746] This is to better reflect that these
+  kinds of errors could be categorised [into newer more specific `ErrorKind`
+  variants][79965], and that they do not represent a user error.
+- [Using environment variable names with `process::Command` on Windows now
+  behaves as expected.][85270] Previously using envionment variables with
+  `Command` would cause them to be ASCII-uppercased.
+- [Rustdoc will now warn on using rustdoc lints that aren't prefixed
+  with `rustdoc::`][86849]
+
+[86849]: https://github.com/rust-lang/rust/pull/86849
+[86513]: https://github.com/rust-lang/rust/pull/86513
+[86334]: https://github.com/rust-lang/rust/pull/86334
+[86260]: https://github.com/rust-lang/rust/pull/86260
+[85970]: https://github.com/rust-lang/rust/pull/85970
+[85876]: https://github.com/rust-lang/rust/pull/85876
+[83572]: https://github.com/rust-lang/rust/pull/83572
+[86294]: https://github.com/rust-lang/rust/pull/86294
+[86858]: https://github.com/rust-lang/rust/pull/86858
+[86761]: https://github.com/rust-lang/rust/pull/86761
+[85769]: https://github.com/rust-lang/rust/pull/85769
+[85746]: https://github.com/rust-lang/rust/pull/85746
+[85305]: https://github.com/rust-lang/rust/pull/85305
+[85270]: https://github.com/rust-lang/rust/pull/85270
+[84111]: https://github.com/rust-lang/rust/pull/84111
+[83918]: https://github.com/rust-lang/rust/pull/83918
+[79965]: https://github.com/rust-lang/rust/pull/79965
+[87370]: https://github.com/rust-lang/rust/pull/87370
+[87298]: https://github.com/rust-lang/rust/pull/87298
+[cargo/9675]: https://github.com/rust-lang/cargo/pull/9675
+[cargo/9550]: https://github.com/rust-lang/cargo/pull/9550
+[cargo/9680]: https://github.com/rust-lang/cargo/pull/9680
+[`array::map`]: https://doc.rust-lang.org/stable/std/primitive.array.html#method.map
+[`Bound::cloned`]: https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.cloned
+[`Drain::as_str`]: https://doc.rust-lang.org/stable/std/string/struct.Drain.html#method.as_str
+[`IntoInnerError::into_error`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_error
+[`IntoInnerError::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_parts
+[`MaybeUninit::assume_init_mut`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_mut
+[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
+[`MaybeUninit::write`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.write
+[`Seek::rewind`]: https://doc.rust-lang.org/stable/std/io/trait.Seek.html#method.rewind
+[`mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
+[`ops::ControlFlow`]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html
+[`str::from_utf8_unchecked`]: https://doc.rust-lang.org/stable/std/str/fn.from_utf8_unchecked.html
+[`x86::_bittest`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittest.html
+[`x86::_bittestandcomplement`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandcomplement.html
+[`x86::_bittestandreset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandreset.html
+[`x86::_bittestandset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandset.html
+[`x86_64::_bittest64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittest64.html
+[`x86_64::_bittestandcomplement64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandcomplement64.html
+[`x86_64::_bittestandreset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandreset64.html
+[`x86_64::_bittestandset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandset64.html
+
+
 Version 1.54.0 (2021-07-29)
 ============================