docs: add day of month to all news-entries

This makes it easier to batch-convert them to other structured
markup-formats.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

docs/index.html

@@ -1546,7 +1546,7 @@ with a new test that does over 130 tests of the
 shading language and built-in functions.
 </p>
 
-<h2>April 2007</h2>
+<h2>April 4, 2007</h2>
 <p>
 Thomas Hellstr&ouml;m of Tungsten Graphics has written a whitepaper
 describing the new DRI memory management system.
@@ -1999,7 +1999,7 @@ Mesa 5.0.2 has been released.  This is a stable, bug-fix release.
 </pre>
 
 
-<h2>June 2003</h2>
+<h2>June 8, 2003</h2>
 
 <p>
 Mesa's directory tree has been overhauled.