github.com/cznic/fileutil: fix FreeBSD build.

Fixes build broken in
https://camlistore.org/gw/01ce3859291e9e012b497af13a4c2dd82d2d1d4f

Change-Id: Ieede30ab41c6896f0b9964895ca7237fa6c34b5a

third_party/github.com/cznic/fileutil/fileutil_freebsd.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2011 CZ.NIC z.s.p.o. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// blame: jnml, labs.nic.cz
+
+package fileutil
+
+import (
+	"os"
+)
+
+// PunchHole deallocates space inside a file in the byte range starting at
+// offset and continuing for len bytes. Unimplemented on FreeBSD
+func PunchHole(f *os.File, off, len int64) error {
+	return nil
+}
+
+// Fadvise predeclares an access pattern for file data.  See also 'man 2
+// posix_fadvise'. Unimplemented on FreeBSD
+func Fadvise(f *os.File, off, len int64, advice FadviseAdvice) error {
+	return nil
+}