This commit adds C support for net package for aix/ppc64.

Change-Id: I704710991fc013c6ec3511671def6791df4854f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/164038
Run-TryBot: Mikio Hara <mikioh.public.networking@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Mikio Hara <mikioh.public.networking@gmail.com>