filelib.php enhancment to support ogv (theora) mime type [PATCH]

Currently, any Ogg/Theora video that is uploaded to Moodle has an unset mime type when downloaded. A simple one-line patch sets the correct mime type on the Ogg/Theora video (files that end in .ogv). This allows those videos to automatically play when viewed by a browser like Firefox 3.5+ that supports Open Video. Furthermore, without this correct mime type, Open Video isn't even possible for those (like me) that are willing to hand code the HTML in, for instance, a web page resource to use the <video> tag and .ogv videos.

After applying the above patch, custom HTML inserted into a new resource -> web page, like:

<video height="480" width="640" tabindex="0" poster="/file.php/1351/MyVideo.jpg" controls="true">
<source src="/file.php/1351/MyVideo.ogv" type="video/ogg" />
<source src="/file.php/1351/MyVideo.mp4" type="video/mp4" />
</video>

Works just fine in Firefox 3.5+, without the patch, Firefox fails to view the video in its built in player.