Rework for syslog version 5. This is a breaking change.

The `syslog` crate underwent extensive API refactoring between versions 3 and 5. This commit rewrites much of `slog-syslog` to fit the new API. It is partially compatible with previous versions of `slog-syslog` (`examples/syslog-unix.rs` still works without modification), but the shape of `Streamer3164` in particular is quite different.

There are also some new features:

* All `SyslogBuilder` settings are now optional and have sensible defaults. Simply running `SyslogBuilder::new().start()` will yield a usable `Drain` (if there is a syslog daemon on the local machine).

* `SyslogBuilder` no longer requires a hostname to be supplied when choosing a transport (TCP, UDP, Unix socket). Instead, the hostname is a separate setting (`SyslogBuilder::hostname`), and if none is provided, it's discovered (if possible) using the `hostname` crate.

* `Streamer3164` no longer contains a mutex, and is not thread-safe (that is, it is no longer `Sync`). This improves performance when used with slog-async, which doesn't need the underlying `Drain` to be thread-safe. `slog::Logger` does require the underlying `Drain` to be thread-safe, so `SyslogBuilder::start` now returns a `Streamer3164` wrapped in a `Mutex`, and there's now a `SyslogBuilder::start_single_threaded` method that returns an unwrapped `Streamer3164` instead.

* Key-value pairs attached to logging records are now, by default, formatted in a style that resembles RFC 5424 STRUCTURED-DATA. Their formatting can be customized by implementing the `MsgFormat3164` trait.

Author: argv-minus-one

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "slog-syslog"
-version = "0.12.0"
+version = "0.13.0"
 authors = ["Dawid Ciężarkiewicz <dpc@dpc.pw>", "William Laeder <codylaeder@gmail.com" ]
 description = "Syslog drain for slog-rs"
 keywords = ["slog", "logging", "json", "log", "syslog"]
@@ -14,6 +14,6 @@ readme = "README.md"
 path = "lib.rs"
 
 [dependencies]
+hostname = "0.3"
 slog = "^2.1.1"
-syslog = "3.3.0"
-nix = "0.14.0"
+syslog = "5.0.0"