unix: add Fstatat on OpenBSD

Also enable TestFstatat for all Unices now that they all implement
Fstatat.

Change-Id: I9722437042d5fc0df4a27d3a6a2be3d124c60057
Reviewed-on: https://go-review.googlesource.com/100617
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/zsyscall_openbsd_arm.go b/unix/zsyscall_openbsd_arm.go
index 2ce02c7..6a7fe67 100644
--- a/unix/zsyscall_openbsd_arm.go
+++ b/unix/zsyscall_openbsd_arm.go
@@ -640,6 +640,21 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
+	var _p0 *byte
+	_p0, err = BytePtrFromString(path)
+	if err != nil {
+		return
+	}
+	_, _, e1 := Syscall6(SYS_FSTATAT, uintptr(fd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Fstatfs(fd int, stat *Statfs_t) (err error) {
 	_, _, e1 := Syscall(SYS_FSTATFS, uintptr(fd), uintptr(unsafe.Pointer(stat)), 0)
 	if e1 != 0 {