[release-branch.go1.8] doc: document go1.8.3

Change-Id: I5d55c3b1011dd10552d8e740fb65886306d91b5c
Reviewed-on: https://go-review.googlesource.com/44035Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-on: https://go-review.googlesource.com/44036

doc/devel/release.html

@@ -56,6 +56,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.8.2">Go
 1.8.2 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.8.3 (released 2017/05/24) includes fixes to the compiler, runtime,
+documentation, and the <code>database/sql</code> package.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.8.3">Go
+1.8.3 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.7">go1.7 (released 2016/08/15)</h2>
 
 <p>