merged scheduled executors GSOC project from Ian Forbed.
Move priority/timed queues to concurrent name space and scheduled executors to executors name spapce.
move scheduled_executor_base.hpp and declare scheduled_thread_pool::worker_loop inline.
Added tyy_pus returning queue_op_status. Rename is_closed to closed.
Added wait_until_not_empty, wait_until_not_empty_or_closed. Rename _q_qempty to _not_empty.
Added sync_queue_base and refactor the concurrent queues to make use of this class. Make other refactor on priority and timed queues.
Removed BOOST_THREAD_QUEUE_DEPRECATE_OLD for priority and timed queues.
Added missing file sync_queue_base and refactor the concurrent queues to make use of this class.
Added move semantics for C++11 compilers. Need of a detail::priority_queue. Tried to do it for C++98, but heap_push/heap_pop algorithms are not move aware:(.
Fix inspection issues.
Fix task exception silently ignored. Make submit throw if closed. join the threads created by the thread_executor
Update executors doc adding thread executor.
Fix inspection issue.
Added not_ready and timeout queue_op_status. Make sync_timed_queue and sync_priority_queue conform to the sync_queue interface. Aapt the test to the new interface.
Remove waiting_empty_.
Avoid locking while doing callback.
Make submit strong-thread safe.
Don't try-catch on try_executing_one_task.
Avoid locking while doing callback.
Minor renamming.