Vendor dependencies

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vendor/log/README.md

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+log
+===
+
+A Rust library providing a lightweight logging *facade*.
+
+[![Build status](https://img.shields.io/github/workflow/status/rust-lang/log/CI/master)](https://github.com/rust-lang/log/actions)
+[![Latest version](https://img.shields.io/crates/v/log.svg)](https://crates.io/crates/log)
+[![Documentation](https://docs.rs/log/badge.svg)](https://docs.rs/log)
+![License](https://img.shields.io/crates/l/log.svg)
+
+* [`log` documentation](https://docs.rs/log)
+
+A logging facade provides a single logging API that abstracts over the actual
+logging implementation. Libraries can use the logging API provided by this
+crate, and the consumer of those libraries can choose the logging
+implementation that is most suitable for its use case.
+
+
+## Minimum supported `rustc`
+
+`1.31.0+`
+
+This version is explicitly tested in CI and may be bumped in any release as needed. Maintaining compatibility with older compilers is a priority though, so the bar for bumping the minimum supported version is set very high. Any changes to the supported minimum version will be called out in the release notes.
+
+## Usage
+
+### In libraries
+
+Libraries should link only to the `log` crate, and use the provided macros to
+log whatever information will be useful to downstream consumers:
+
+```toml
+[dependencies]
+log = "0.4"
+```
+
+```rust
+use log::{info, trace, warn};
+
+pub fn shave_the_yak(yak: &mut Yak) {
+    trace!("Commencing yak shaving");
+
+    loop {
+        match find_a_razor() {
+            Ok(razor) => {
+                info!("Razor located: {}", razor);
+                yak.shave(razor);
+                break;
+            }
+            Err(err) => {
+                warn!("Unable to locate a razor: {}, retrying", err);
+            }
+        }
+    }
+}
+```
+
+### In executables
+
+In order to produce log output, executables have to use a logger implementation compatible with the facade.
+There are many available implementations to choose from, here are some of the most popular ones:
+
+* Simple minimal loggers:
+    * [`env_logger`](https://docs.rs/env_logger/*/env_logger/)
+    * [`simple_logger`](https://docs.rs/simple_logger/*/simple_logger/)
+    * [`simplelog`](https://docs.rs/simplelog/*/simplelog/)
+    * [`pretty_env_logger`](https://docs.rs/pretty_env_logger/*/pretty_env_logger/)
+    * [`stderrlog`](https://docs.rs/stderrlog/*/stderrlog/)
+    * [`flexi_logger`](https://docs.rs/flexi_logger/*/flexi_logger/)
+* Complex configurable frameworks:
+    * [`log4rs`](https://docs.rs/log4rs/*/log4rs/)
+    * [`fern`](https://docs.rs/fern/*/fern/)
+* Adaptors for other facilities:
+    * [`syslog`](https://docs.rs/syslog/*/syslog/)
+    * [`systemd-journal-logger`](https://docs.rs/systemd-journal-logger/*/systemd_journal_logger/)
+    * [`slog-stdlog`](https://docs.rs/slog-stdlog/*/slog_stdlog/)
+    * [`android_log`](https://docs.rs/android_log/*/android_log/)
+    * [`win_dbg_logger`](https://docs.rs/win_dbg_logger/*/win_dbg_logger/)
+    * [`db_logger`](https://docs.rs/db_logger/*/db_logger/)
+* For WebAssembly binaries:
+    * [`console_log`](https://docs.rs/console_log/*/console_log/)
+* For dynamic libraries:
+    * You may need to construct [an FFI-safe wrapper over `log`](https://github.com/rust-lang/log/issues/421) to initialize in your libraries. 
+* Utilities:
+    * [`log_err`](https://docs.rs/log_err/*/log_err/)
+
+Executables should choose a logger implementation and initialize it early in the
+runtime of the program. Logger implementations will typically include a
+function to do this. Any log messages generated before the logger is
+initialized will be ignored.
+
+The executable itself may use the `log` crate to log as well.
+
+## Structured logging
+
+If you enable the `kv_unstable` feature, you can associate structured data with your log records:
+
+```rust
+use log::{info, trace, warn, as_serde, as_error};
+
+pub fn shave_the_yak(yak: &mut Yak) {
+    trace!(target = "yak_events", yak = as_serde!(yak); "Commencing yak shaving");
+
+    loop {
+        match find_a_razor() {
+            Ok(razor) => {
+                info!(razor = razor; "Razor located");
+                yak.shave(razor);
+                break;
+            }
+            Err(err) => {
+                warn!(err = as_error!(err); "Unable to locate a razor, retrying");
+            }
+        }
+    }
+}
+```