[m-rev.] for review: Change interface of closeable_channel.try_take.

[Julien Fischer]

On Fri, 17 Apr 2020, Peter Wang wrote:

> library/thread.closeable_channel.m:
>    Rename the `empty' result of closeable_channel.try_take to
>    `would_block'.
>
> tests/hard_coded/closeable_channel_test.exp:
> tests/hard_coded/closeable_channel_test.m:
>    Update test case.

That's fine.

Julien.