doc/go1.5.txt: mention zip.WriterAt

Change-Id: I9f5ca101e0d2fe71cb1ca810cfeeb82c12f5f8e7
Reviewed-on: https://go-review.googlesource.com/7491
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/doc/go1.5.txt b/doc/go1.5.txt
index 5aa34b8..3f22496 100644
--- a/doc/go1.5.txt
+++ b/doc/go1.5.txt
@@ -7,6 +7,7 @@
 
 API additions and behavior changes:
 
+archive/zip: add WriterAt function (https://golang.org/cl/7445)
 bufio: add Reader.Discard (https://golang.org/cl/2260)
 crypto/cipher: clarify what will happen if len(src) != len(dst) for the Stream interface. (https://golang.org/cl/1754)
 crypto/elliptic: add Name field to CurveParams struct (https://golang.org/cl/2133)