Vendor things

third-party/vendor/crossbeam-epoch/README.md

@@ -0,0 +1,53 @@
+# Crossbeam Epoch
+
+[![Build Status](https://github.com/crossbeam-rs/crossbeam/workflows/CI/badge.svg)](
+https://github.com/crossbeam-rs/crossbeam/actions)
+[![License](https://img.shields.io/badge/license-MIT_OR_Apache--2.0-blue.svg)](
+https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-epoch#license)
+[![Cargo](https://img.shields.io/crates/v/crossbeam-epoch.svg)](
+https://crates.io/crates/crossbeam-epoch)
+[![Documentation](https://docs.rs/crossbeam-epoch/badge.svg)](
+https://docs.rs/crossbeam-epoch)
+[![Rust 1.61+](https://img.shields.io/badge/rust-1.61+-lightgray.svg)](
+https://www.rust-lang.org)
+[![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
+
+This crate provides epoch-based garbage collection for building concurrent data structures.
+
+When a thread removes an object from a concurrent data structure, other threads
+may be still using pointers to it at the same time, so it cannot be destroyed
+immediately. Epoch-based GC is an efficient mechanism for deferring destruction of
+shared objects until no pointers to them can exist.
+
+Everything in this crate except the global GC can be used in `no_std` environments, provided that
+`alloc` feature is enabled.
+
+## Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+crossbeam-epoch = "0.9"
+```
+
+## Compatibility
+
+Crossbeam Epoch supports stable Rust releases going back at least six months,
+and every time the minimum supported Rust version is increased, a new minor
+version is released. Currently, the minimum supported Rust version is 1.61.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+#### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.