Thread::Queue: Hold mutex lock for CV notifications
Thread::Queue: Hold mutex lock for CV notifications

This appears to prevent thread deadlocking on Windows, even though C\+\+ documentation claims that it isn't required.

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3