doc: update go1.11 release notes

Change-Id: I3e2a19fe90334f0c1ed1593c7a9a3a458f15d8e8
Reviewed-on: https://go-review.googlesource.com/124799Reviewed-by: Andrew Bonventre <andybons@golang.org>

doc/go1.11.html

@@ -463,7 +463,8 @@ for k := range m {
 <dl id="encoding/asn1"><dt><a href="/pkg/encoding/asn1/">encoding/asn1</a></dt>
   <dd>
     <p><!-- CL 110561 -->
-      <code>Marshal</code> and <code>Unmarshal</code> now support private class annotations for fields.
+      <code>Marshal</code> and <code><a href="/pkg/encoding/asn1/#Unmarshal">Unmarshal</a></code>
+      now support "private" class annotations for fields.
     </p>
 
 </dl><!-- encoding/asn1 -->