protect the use of && when BOOST_NO_CXX11_RVALUE_REFERENCES is defined.
Restore breaking change.
don't close the queue when an exception is throw, don't return empty on wait_pull_pull_front.
don't close the queue when an exception is throw, don't return empty on wait_pull_pull_front.
Merge branch 'develop' of https://github.com/boostorg/thread into gettickcount64_clean