docs: update calendar, add news and link release notes to 17.3.7

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>

docs/index.html

@@ -16,6 +16,12 @@
 
 <h1>News</h1>
 
+<h2>March 21, 2018</h2>
+<p>
+<a href="relnotes/17.3.7.html">Mesa 17.3.7</a> is released.
+This is a bug-fix release.
+</p>
+
 <h2>February 26, 2018</h2>
 <p>
 <a href="relnotes/17.3.6.html">Mesa 17.3.6</a> is released.

docs/release-calendar.html

@@ -39,13 +39,7 @@ if you'd like to nominate a patch in the next stable release.
 <th>Notes</th>
 </tr>
 <tr>
-<td rowspan="3">17.3</td>
-<td>2018-03-09</td>
-<td>17.3.7</td>
-<td>Juan A. Suarez Romero</td>
-<td></td>
-</tr>
-<tr>
+<td rowspan="2">17.3</td>
 <td>2018-03-23</td>
 <td>17.3.8</td>
 <td>Juan A. Suarez Romero</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/17.3.7.html">17.3.7 release notes</a>
 <li><a href="relnotes/17.3.6.html">17.3.6 release notes</a>
 <li><a href="relnotes/17.3.5.html">17.3.5 release notes</a>
 <li><a href="relnotes/17.3.4.html">17.3.4 release notes</a>