unix: replace "mksyscall_aix_ppc64.pl" script with a Go program

Port mksyscall_aix_ppc64.pl Perl script to mksyscall_aix_ppc64.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: Ie888c0df470dcfc75034faa12cf3422b2d426629
Reviewed-on: https://go-review.googlesource.com/c/158699
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

unix/mkall.sh

@@ -67,7 +67,7 @@ aix_ppc)
 	;;
 aix_ppc64)
 	mkerrors="$mkerrors -maix64"
-	mksyscall="./mksyscall_aix_ppc64.pl -aix"
+	mksyscall="go run mksyscall_aix_ppc64.go -aix"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 darwin_386)

unix/zsyscall_aix_ppc64.go

-// mksyscall_aix_ppc64.pl -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
+// go run mksyscall_aix_ppc64.go -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
 // +build aix,ppc64

unix/zsyscall_aix_ppc64_gc.go

-// mksyscall_aix_ppc64.pl -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
+// go run mksyscall_aix_ppc64.go -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
 // +build aix,ppc64

unix/zsyscall_aix_ppc64_gccgo.go

-// mksyscall_aix_ppc64.pl -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
+// go run mksyscall_aix_ppc64.go -aix -tags aix,ppc64 syscall_aix.go syscall_aix_ppc64.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
 // +build aix,ppc64