C++11多线程（二）：this_thread 名字空间

     C++ 11的 std::this_thread名字实现了很多线程辅助函数，例如get_id(),  yeild()等，this_thread代码如下：

namespace this_thread {
thread::id get_id() _NOEXCEPT;

inline void yield() _NOEXCEPT
	{	// give up balance of time slice
	_Thrd_yield();
	}

inline void sleep_until(const stdext::threads::xtime *_Abs_time)
	{	// sleep until _Abs_time
	_Thrd_sleep(_Abs_time);
	}

template inline
	void sleep_until(
		const chrono::time_point& _Abs_time)
	{	// sleep until time point
	stdext::threads::xtime _Tgt;
	_Tgt.sec = chrono::duration_cast(
		_Abs_time.time_since_epoch()).count();
	_Tgt.nsec = (long)chrono::duration_cast(
		_Abs_time.time_since_epoch() - chrono::seconds(_Tgt.sec)).count();
	sleep_until(&_Tgt);
	}

template inline
	void sleep_for(const chrono::duration&a