Thread: Added first version of sync_queue.

git-svn-id: http://svn.boost.org/svn/boost/trunk@83547 b8fc166d-592f-0410-95f2-cb63ce0dd405
Thread: avoid the use of boost/thread/thread.hpp to limit dependencies.

git-svn-id: http://svn.boost.org/svn/boost/trunk@83548 b8fc166d-592f-0410-95f2-cb63ce0dd405