doc: document go1.4.3

Change-Id: Ib1bfe4038e2b125a31acd9ff7772e462b0a6358f
Reviewed-on: https://go-review.googlesource.com/14852Reviewed-by: Andrew Gerrand <adg@golang.org>

doc/devel/release.html

@@ -48,6 +48,11 @@ go1.4.2 (released 2015/02/17) includes bug fixes to the <code>go</code> command,
 See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.4.2">Go 1.4.2 milestone on our issue tracker</a> for details.
 </p>
 
+<p>
+go1.4.3 (released 2015/09/22) includes security fixes to the <code>net/http</code> package and bug fixes to the <code>runtime</code> package.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.4.3">Go 1.4.3 milestone on our issue tracker</a> for details.
+</p>
+
 <h2 id="go1.3">go1.3 (released 2014/06/18)</h2>
 
 <p>