Port mksyscall_aix_ppc.pl Perl script to mksyscall_aix_ppc.go.
mkall.sh script is modified to run mksyscall.go. Running
mkall.sh does not generate any git diff besides the command
name in comments of generated files.

Updates golang/go#27779

Change-Id: I57b0e5f9fe44dadd96d0e512046bb63e8e1b9f66
Reviewed-on: https://go-review.googlesource.com/c/156778Reviewed-by: Clément Chigot <clement.chigot@atos.net>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>