remove cruft from pthread structure (old cancellation stuff)

src/internal/pthread_impl.h

@@ -27,8 +27,6 @@ struct pthread {
 	uintptr_t canary;
 	pid_t tid, pid;
 	int tsd_used, errno_val, *errno_ptr;
-	/* All cancellation-related fields must remain together, in order */
-	volatile uintptr_t cp_sp, cp_ip;
 	volatile int cancel, canceldisable, cancelasync;
 	unsigned char *map_base;
 	size_t map_size;