This commit add port of runtime/cgo for aix/ppc64.
AIX assembly is different from Linux assembly, therefore gcc_ppc64.S
must be redone for AIX.

Change-Id: I780ebab4ef9c4ce912f4c4d521d8c135b1eebf6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/164002
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>