- Use `Handle::default` over `Handle::current` for consistent semantics
- Make all `windows::Event` constructors lazily invoke `global_init`
so they can be safely constructed off-task
- Don't assume the reactor is alive and event registration will be done
when calling `global_init`
Add windows regression tests. Unfortunately, Windows doesn't have a
reliable way of programmatically sending CTRL_C or CTRL_BREAK events
to a progress, so the tests can only exercise our internal machinery by
invoking the handler that we register with the OS
Fixes#999
* Don't use tokio-core any more for tests. That one brings tokio from
crates.io instead of the current workspace and two versions of that
don't want to cooperate.
* Guard unix-specific examples on windows.
* Leave CI setup to top-level directory.