Fixing regression bug 163191. Unable to resize columns in Subscribe.

r=timeless, sr=sspitzer

mailnews/base/resources/content/subscribe.xul

@@ -137,8 +137,10 @@ Rights Reserved.
           <treecols id="theSubscribeColumns">
             <treecol id="nameColumn" persist="hidden" flex="1" primary="true" label="..."
                      sort="?LeafName"/>
+            <splitter class="tree-splitter"/>
             <treecol id="subscribedColumn" persist="hidden" label="&subscribedHeader.label;"
                      sort="?Subscribed"/>
+            <splitter class="tree-splitter"/>
             <treecol id="messagesColumn" persist="hidden" label="&messagesHeader.label;"
                      sort="?TotalMessages"/>
           </treecols>
@@ -151,7 +153,9 @@ Rights Reserved.
               onclick="SearchOnClick(event);"> 
          <treecols>
            <treecol id="nameColumn2" persist="hidden" flex="1" primary="true" label="..." />
+           <splitter class="tree-splitter"/>
            <treecol id="subscribedColumn2" persist="hidden" label="&subscribedHeader.label;" />
+           <splitter class="tree-splitter"/>
            <treecol id="messagesColumn2" persist="hidden" label="&messagesHeader.label;" />
          </treecols>
          <treechildren id="searchTreeBody"/>