Vendor dependencies for 0.3.0 release

vendor/polling/README.md

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+# polling
+
+[![Build](https://github.com/smol-rs/polling/actions/workflows/ci.yml/badge.svg)](
+https://github.com/smol-rs/polling/actions)
+[![License](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](
+https://github.com/smol-rs/polling)
+[![Cargo](https://img.shields.io/crates/v/polling.svg)](
+https://crates.io/crates/polling)
+[![Documentation](https://docs.rs/polling/badge.svg)](
+https://docs.rs/polling)
+
+Portable interface to epoll, kqueue, event ports, and IOCP.
+
+Supported platforms:
+- [epoll](https://en.wikipedia.org/wiki/Epoll): Linux, Android, RedoxOS
+- [kqueue](https://en.wikipedia.org/wiki/Kqueue): macOS, iOS, tvOS, watchOS, visionOS, FreeBSD, NetBSD, OpenBSD,
+  DragonFly BSD
+- [event ports](https://illumos.org/man/port_create): illumos, Solaris
+- [poll](https://en.wikipedia.org/wiki/Poll_(Unix)): VxWorks, Fuchsia, HermitOS, other Unix systems
+- [IOCP](https://learn.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports): Windows, Wine (version 7.13+)
+
+By default, polling is done in oneshot mode, which means interest in I/O events needs to
+be re-enabled after an event is delivered if we're interested in the next event of the same
+kind. However, level and edge triggered modes are also available for certain operating
+systems. See the documentation of the [`PollMode`] type for more information.
+
+Only one thread can be waiting for I/O events at a time.
+
+[`PollMode`]: https://docs.rs/polling/latest/polling/enum.PollMode.html
+
+## Examples
+
+```rust,no_run
+use polling::{Event, Poller};
+use std::net::TcpListener;
+
+// Create a TCP listener.
+let socket = TcpListener::bind("127.0.0.1:8000")?;
+socket.set_nonblocking(true)?;
+let key = 7; // Arbitrary key identifying the socket.
+
+// Create a poller and register interest in readability on the socket.
+let poller = Poller::new()?;
+poller.add(&socket, Event::readable(key))?;
+
+// The event loop.
+let mut events = Vec::new();
+loop {
+    // Wait for at least one I/O event.
+    events.clear();
+    poller.wait(&mut events, None)?;
+
+    for ev in &events {
+        if ev.key == key {
+            // Perform a non-blocking accept operation.
+            socket.accept()?;
+            // Set interest in the next readability event.
+            poller.modify(&socket, Event::readable(key))?;
+        }
+    }
+}
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/license/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.