Update.
* descr.h: Define CANCELING_BIT and CANCELING_BITMASK. Introduce
after CANCELTYPE_BIT, move the other bits up. Update CANCEL_RESTMASK.
* init.c (sigcancel_handler): Also set CANCELING_BITMASK bit in newval.
* pthread_cancel.c (pthread_cancel): Likewise. Also set CANCELING_BIT
if asynchronous canceling is enabled.
* pthread_join.c (pthread_join): When recognizing circular joins,
take into account the other thread might be already canceled.
* Makefile (tests): Add tst-join5.
* tst-join5.c: New file.