_thr_leave_cancellation_point to _thr_cancel_leave, add a parameter
to _thr_cancel_leave to indicate whether cancellation point should be
checked, this gives us an option to not check cancallation point if
a syscall successfully returns to avoid any leaks, current I have
creat(), open() and fcntl(F_DUPFD) to not check cancellation point
after they sucessfully returned.
Replace some members in structure kse with bit flags to same some
memory.
Conditionally compile THR_ASSERT to nothing if _PTHREAD_INVARIANTS is
not defined.
Inline some small functions in thr_cancel.c.
Use __predict_false in thr_kern.c for some executed only once code.
Reviewd by: deischen
71679e629d