Vendor things

third-party/vendor/backtrace/README.md

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+# backtrace-rs
+
+[Documentation](https://docs.rs/backtrace)
+
+A library for acquiring backtraces at runtime for Rust. This library aims to
+enhance the support of the standard library by providing a programmatic
+interface to work with, but it also supports simply easily printing the current
+backtrace like libstd's panics.
+
+## Install
+
+```toml
+[dependencies]
+backtrace = "0.3"
+```
+
+## Usage
+
+To simply capture a backtrace and defer dealing with it until a later time,
+you can use the top-level `Backtrace` type.
+
+```rust
+use backtrace::Backtrace;
+
+fn main() {
+    let bt = Backtrace::new();
+
+    // do_some_work();
+
+    println!("{:?}", bt);
+}
+```
+
+If, however, you'd like more raw access to the actual tracing functionality, you
+can use the `trace` and `resolve` functions directly.
+
+```rust
+fn main() {
+    backtrace::trace(|frame| {
+        let ip = frame.ip();
+        let symbol_address = frame.symbol_address();
+
+        // Resolve this instruction pointer to a symbol name
+        backtrace::resolve_frame(frame, |symbol| {
+            if let Some(name) = symbol.name() {
+                // ...
+            }
+            if let Some(filename) = symbol.filename() {
+                // ...
+            }
+        });
+
+        true // keep going to the next frame
+    });
+}
+```
+
+# License
+
+This project is 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/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in backtrace-rs by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.