When spawning using `Handle` while on the executor, tasks were being
double counted. This prevented the number of active tasks to reach zero,
thus preventing the executor from shutting down.
This changes `spawn` to check if being called from the executor
**before** incrementing the number of active tasks.
Fixes#760
Previously, every call to `current_thread::Handle::spawn` would go
through a `mpsc` channel. This is unnecessary when the `Handle` is still
on the same thread as the current thread executor. This patch fixes that
by storing the `ThreadId` of the executor when it is created, and then
comparing against that when `Handle::spawn` is called. If the call is
made from the same thread, `spawn_local` is used directly.
Fixes#562.
The futures 0.2 crate is not intended for widespread usage. Also, the
futures team is exploring the compat shim route.
If futures 0.3 support is added to Tokio 0.1, then a different
integration route will be explored, making the current code unhelpful.
Extract `tokio::executor::current_thread` to a tokio-current-thread
crate. Deprecated fns stay in the old location. The new crate only
contains thee most recent API.
