docs: update calendar, add news item and link release notes for 17.3.1

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>

docs/index.html

@@ -16,6 +16,12 @@
 
 <h1>News</h1>
 
+<h2>December 21, 2017</h2>
+<p>
+<a href="relnotes/17.3.1.html">Mesa 17.3.1</a> is released.
+This is a bug-fix release.
+</p>
+
 <h2>December 14, 2017</h2>
 <p>
 <a href="relnotes/17.2.7.html">Mesa 17.2.7</a> is released.

docs/release-calendar.html

@@ -46,13 +46,7 @@ if you'd like to nominate a patch in the next stable release.
 <td>Final planned release for the 17.2 series</td>
 </tr>
 <tr>
-<td rowspan="6">17.3</td>
-<td>2017-12-15</td>
-<td>17.3.1</td>
-<td>Emil Velikov</td>
-<td></td>
-</tr>
-<tr>
+<td rowspan="5">17.3</td>
 <td>2017-12-29</td>
 <td>17.3.2</td>
 <td>Emil Velikov</td>

docs/relnotes.html

@@ -21,6 +21,7 @@ The release notes summarize what's new or changed in each Mesa release.
 </p>
 
 <ul>
+<li><a href="relnotes/17.3.1.html">17.3.1 release notes</a>
 <li><a href="relnotes/17.2.7.html">17.2.7 release notes</a>
 <li><a href="relnotes/17.3.0.html">17.3.0 release notes</a>
 <li><a href="relnotes/17.2.6.html">17.2.6 release notes</a>