syscall: fix coredump bit for aix/ppc64

Change-Id: I92173c3b5f842b829aac7c4d7abbe8b5113e530a
Reviewed-on: https://go-review.googlesource.com/c/go/+/191787
Run-TryBot: Clément Chigot <clement.chigot@atos.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

src/syscall/syscall_aix.go

@@ -494,7 +494,7 @@ func (w WaitStatus) Signal() Signal {
 
 func (w WaitStatus) Continued() bool { return w&0x01000000 != 0 }
 
-func (w WaitStatus) CoreDump() bool { return w&0x200 == 0 }
+func (w WaitStatus) CoreDump() bool { return w&0x80 == 0x80 }
 
 func (w WaitStatus) TrapCause() int { return -1 }