Changes since 1.0.0:
- Added the `Handle::wait_timeout` and `Handle::wait_deadline` methods.
These are gated by the `timeout` feature, which is enabled by default.
Windows supports these timeouts natively, but on Unix this requires
handling `SIGCHLD`.
- Fixed a bug with setting or removing non-uppercase env var names on
Windows. Duct previously uppercased all env var names passed to its
API, but not names coming from the system environment, which caused
mismatches. See https://github.com/oconnor663/duct.rs/pull/119.
Contributed by @Wazzaps.