doc: document go1.9

Change-Id: I97075f24319a4b96cbeb9e3ff2e7b2056ff59e32
Reviewed-on: https://go-review.googlesource.com/58651Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/devel/release.html

@@ -20,7 +20,14 @@ For example, Go 1.8 is supported until Go 1.10 is released,
 and Go 1.9 is supported until Go 1.11 is released.
 We fix critical problems, including <a href="/security">critical security problems</a>,
 in supported releases as needed by issuing minor revisions
-(for example, Go 1.8.1, Go 1.8.2, and so on).
+(for example, Go 1.9.1, Go 1.9.2, and so on).
+</p>
+
+<h2 id="go1.9">go1.9 (released 2017/08/24)</h2>
+
+<p>
+Go 1.9 is a major release of Go.
+Read the <a href="/doc/go1.9">Go 1.9 Release Notes</a> for more information.
 </p>
 
 <h2 id="go1.8">go1.8 (released 2017/02/16)</h2>

doc/go1.9.html

@@ -15,12 +15,7 @@ Do not send CLs removing the interior tags from such phrases.
 ul li { margin: 0.5em 0; }
 </style>
 
-<h2 id="introduction">DRAFT RELEASE NOTES - Introduction to Go 1.9</h2>
-
-<p><strong>
-    Go 1.9 is not yet released. These are work-in-progress
-    release notes. Go 1.9 is expected to be released in August 2017.
-</strong></p>
+<h2 id="introduction">Introduction to Go 1.9</h2>
 
 <p>
   The latest Go release, version 1.9, arrives six months

doc/install-source.html

@@ -221,7 +221,7 @@ To build without <code>cgo</code>, set the environment variable
 Change to the directory that will be its parent
 and make sure the <code>go</code> directory does not exist.
 Then clone the repository and check out the latest release tag
-(<code class="versionTag">go1.8.1</code>, for example):</p>
+(<code class="versionTag">go1.9</code>, for example):</p>
 
 <pre>
 $ git clone https://go.googlesource.com/go
@@ -409,7 +409,7 @@ New releases are announced on the
 <a href="//groups.google.com/group/golang-announce">golang-announce</a>
 mailing list.
 Each announcement mentions the latest release tag, for instance,
-<code class="versionTag">go1.8.1</code>.
+<code class="versionTag">go1.9</code>.
 </p>
 
 <p>