Lock worker when adding tasks to the queue

This sole hunk has been extracted from:
https://github.com/abilian/cythonplus-sandbox/commit/a3743de8437e482720c1f441d5a019f18a390df1.patchCo-authored-by: Jerome Dumonteil <jd@abilian.com>
Co-authored-by: Xavier Thompson <xavier.thompson@nexedi.com>

runtime.pxd

@@ -44,7 +44,8 @@ cdef inline void * worker_function(void * arg) nogil:
                 # Discard the empty queue and continue the main loop.
                 continue
         # The queue is not empty: reinsert it in this worker's queues.
-        worker.queues.push_back(queue)
+        with wlocked worker:
+            worker.queues.push_back(queue)
         # Signal that the queue is available.
         sem_post(&sch.num_free_queues)