Update release notes

[jens-mueller-sociomantic]

This change adds missing release notes for the upcoming release. Specifically, it provides release notes for the notifyShutdown function introduced in commit 76d8e95 and the breaking changes to the NDArray.data method introduced in commit 5f378b4. We also mention that dmxnet supports now multi-threaded MXNet engines (used to be only the single-threaded NaiveEngine) which is largely a result of the above mentioned changes to NDArray.data. The tests should pass for any MXNet engines (see commit 16fdf80). We also mention that there is still a race on process exit that has been only partly addressed by using the introduced notifyShutdown function (see commit f8b1c9a).

[jens-mueller-sociomantic]

@joseph-wakeling-sociomantic From the changes since the last release I only found these to be relevant. One could argue to include that non-single-threaded engines can be used now. Not sure.

[joseph-wakeling-sociomantic]

Isn't it the synchronized read/write that should unlock that? We could add a note that this removes a blocker to using multithreaded engines. But IIRC we do still have an open issue about the multithreaded case.

[jens-mueller-sociomantic]

Yes, I'd like to add a note that multi-threaded engines can be used. But should this be a feature or part of the synchronized read-only release notes? Do you mean sociomantic-tsunami/dmxnet#66?

[jens-mueller-sociomantic]

Of course, we can also leave this out if it looks sufficient to you.

[joseph-wakeling-sociomantic]

Let's add a separate note, and cross-ref the changes that made this possible.

[joseph-wakeling-sociomantic]

And yes, by "open issue" I mean https://github.com/sociomantic-tsunami/dmxnet/issues/66.

[joseph-wakeling-sociomantic]

Apart from the one typo, LGTM.

[jens-mueller-sociomantic]

diff --git a/relnotes/multithreaded-engines.feature.md b/relnotes/multithreaded-engines.feature.md
index fb7f701..45b1ed9 100644
--- a/relnotes/multithreaded-engines.feature.md
+++ b/relnotes/multithreaded-engines.feature.md
@@ -4,7 +4,7 @@

 The changes to `NDArray.data` along with its required migrations enable the use
 of multi-threaded MXNet engines. Unit and integration tests pass for all
-engines and the restriction to the single-threaded `NaiveEngine` has be
+engines and the restriction to the single-threaded `NaiveEngine` has been
 removed. Note though, that on process exit there is still a race after
 executing unittests. The race is likely to be caused by dmxnet interacting with
 MXNet while MXNet is cleaning up at process exit. This issue is still open and