linux下被定义为：

在linux履行pthread_t它被定义为 "unsigned long int",参考这里

Windows下这样定义：

    /*

     * Generic handle type - intended to extend uniqueness beyond

     * that available with a simple pointer. It should scale for either

     * IA-32 or IA-64.

     */

    typedef struct {

        void * p;                   /* Pointer to actual object */

        unsigned int x;             /* Extra information - reuse count etc */

    } ptw32_handle_t;

    typedef ptw32_handle_t pthread_t;