utils: add a thread-safe single-producer/single-consumer queue

[sebsura]

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Adds utilities and data structures that can be used safely in multi-threaded code.

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[arogge]

This looks great. However, I still have a lot of comments, ideas and wishes. Feel free to discuss.
I haven't looked at the test yet.

[arogge]

I have left a few comments for the test. My main concern is randomness and reproducibility.
The "end-user" API is pretty neat btw.

[arogge]

Great stuff. Thank you!