make keyboard tab switching work when the url bar is focused. Patch by

neil@parkwaycc.co.uk, r=jesse, sr=jag, a=asa

suite/browser/tabbrowser.xml

@@ -51,7 +51,7 @@
 
     <content>
       <xul:stringbundle src="chrome://global/locale/tabbrowser.properties"/>
-      <xul:tabbox flex="1"
+      <xul:tabbox flex="1" eventnode="document"
                   onselect="if (!('updateCurrentBrowser' in this.parentNode) || event.target.localName != 'tabpanels') return; this.parentNode.updateCurrentBrowser();">
         <xul:hbox class="tabbrowser-strip chromeclass-toolbar" collapsed="true" tooltip="_child" context="_child">
           <xul:tooltip onpopupshowing="event.preventBubble(); if (document.tooltipNode.hasAttribute('label')) { this.setAttribute('label', document.tooltipNode.getAttribute('label')); return true; } return false;"/>