Revert "remove usage of tbb::concurrent_queue, as it seems to be less immune to race conditions than the other implementation (?)"
Revert "remove usage of tbb::concurrent_queue, as it seems to be less immune to race conditions than the other implementation (?)"

This reverts commit 5f222d75dd894156e8e2f90f7a4530d1819c1cef.

manpen/thrill,manpen/thrill,manpen/thrill,manpen/thrill,manpen/thrill