Fix wrong PTHREAD_CANCEL_ASYNCHRONOUS on FreeBSD and OpenBSD

The test runner was deadlocking when a test raised a signal on FreeBSD.

This is untested on OpenBSD, but I have referenced this file:
https://github.com/openbsd/src/blob/master/include/pthread.h

core/sys/unix/pthread_freebsd.odin

@@ -95,7 +95,7 @@ sem_t :: struct {
 PTHREAD_CANCEL_ENABLE       :: 0
 PTHREAD_CANCEL_DISABLE      :: 1
 PTHREAD_CANCEL_DEFERRED     :: 0
-PTHREAD_CANCEL_ASYNCHRONOUS :: 1
+PTHREAD_CANCEL_ASYNCHRONOUS :: 2
 
 foreign import "system:pthread"
 
@@ -119,4 +119,4 @@ foreign pthread {
 	pthread_setcancelstate :: proc (state: c.int, old_state: ^c.int) -> c.int ---
 	pthread_setcanceltype  :: proc (type:  c.int, old_type:  ^c.int) -> c.int ---
 	pthread_cancel         :: proc (thread: pthread_t) -> c.int ---
-}
+}