Menu: Use start icon (first is deprecated)

Author: jzaefferer

demos/menu/icons.html

@@ -29,7 +29,7 @@
 	<li>
 		<a href="#">Playback</a>
 		<ul>
-			<li><a href="#"><span class="ui-icon ui-icon-seek-first"></span>Prev</a></li>
+			<li><a href="#"><span class="ui-icon ui-icon-seek-start"></span>Prev</a></li>
 			<li><a href="#"><span class="ui-icon ui-icon-stop"></span>Stop</a></li>
 			<li><a href="#"><span class="ui-icon ui-icon-play"></span>Play</a></li>
 			<li><a href="#"><span class="ui-icon ui-icon-seek-end"></span>Next</a></li>