[release-branch.go1.7] doc: document go1.7.5

Change-Id: Ic8d4e971edebba9412f2e7c3d3c29f296c4977ff
Reviewed-on: https://go-review.googlesource.com/35833Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-on: https://go-review.googlesource.com/35835Reviewed-by: Chris Broadfoot <cbro@golang.org>

doc/devel/release.html

@@ -69,6 +69,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.7.4">Go
 1.7.4 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.7.5 (released 2017/01/26) includes fixes to the compiler, runtime,
+and the <code>crypto/x509</code> and <code>time</code> packages.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.7.5">Go
+1.7.5 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.6">go1.6 (released 2016/02/17)</h2>
 
 <p>