os: use opendir64 and closedir64 on AIX

When using readdir64 on AIX, we must also use
opendir64 and closedir64.

Issue golang/go#19200

Change-Id: I14211a0bba0bf0c848568c4ae9d3821bcbc2c353
Reviewed-on: https://go-review.googlesource.com/43251
Reviewed-by: Ian Lance Taylor <iant@golang.org>

libgo/go/os/dir_gccgo.go

diff --git a/libgo/go/os/dir_gccgo.go b/libgo/go/os/dir_gccgo.go
index 8923f0e..f660646 100644
--- a/libgo/go/os/dir_gccgo.go
+++ b/libgo/go/os/dir_gccgo.go
@@ -12,12 +12,6 @@
 	"unsafe"
 )
 
-//extern opendir
-func libc_opendir(*byte) *syscall.DIR
-
-//extern closedir
-func libc_closedir(*syscall.DIR) int
-
 // FIXME: pathconf returns long, not int.
 //extern pathconf
 func libc_pathconf(*byte, int) int

libgo/go/os/dir_libc64_gccgo.go

diff --git a/libgo/go/os/dir_libc64_gccgo.go b/libgo/go/os/dir_libc64_gccgo.go
new file mode 100644
index 0000000..95d4663
--- /dev/null
+++ b/libgo/go/os/dir_libc64_gccgo.go
@@ -0,0 +1,15 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix
+
+package os
+
+import "syscall"
+
+//extern opendir64
+func libc_opendir(*byte) *syscall.DIR
+
+//extern closedir64
+func libc_closedir(*syscall.DIR) int

libgo/go/os/dir_libc_gccgo.go

diff --git a/libgo/go/os/dir_libc_gccgo.go b/libgo/go/os/dir_libc_gccgo.go
new file mode 100644
index 0000000..1ee253c
--- /dev/null
+++ b/libgo/go/os/dir_libc_gccgo.go
@@ -0,0 +1,15 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !aix
+
+package os
+
+import "syscall"
+
+//extern opendir
+func libc_opendir(*byte) *syscall.DIR
+
+//extern closedir
+func libc_closedir(*syscall.DIR) int