singleTile overlays repeating when base layer has wrapDateLine false

When the baseLayer has wrapDateLine false, it doesn't repeat when we show more than the world. However, singleTile overlays don't listen to this, and will repeat.

Here is an example to reproduce:

```
<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <link rel="stylesheet" href="../theme/default/style.css" type="text/css">
    <link rel="stylesheet" href="style.css" type="text/css">
    <script src="../lib/OpenLayers.js"></script>
    <script type="text/javascript">
        var map, layer;

        function init(){
            map = new OpenLayers.Map( 'map', {projection: "EPSG:900913"} );
            map.addLayer(new OpenLayers.Layer.XYZ(
            "Imagery",
            [
                "http://otile1.mqcdn.com/tiles/1.0.0/sat/${z}/${x}/${y}.png",
                "http://otile2.mqcdn.com/tiles/1.0.0/sat/${z}/${x}/${y}.png",
                "http://otile3.mqcdn.com/tiles/1.0.0/sat/${z}/${x}/${y}.png",
                "http://otile4.mqcdn.com/tiles/1.0.0/sat/${z}/${x}/${y}.png"
            ],
            {
                attribution: "Tiles Courtesy of <a href='http://open.mapquest.co.uk/' target='_blank'>MapQuest</a>. Portions Courtesy NASA/JPL-Caltech and U.S. Depart. of Agriculture, Farm Service Agency. <img src='http://developer.mapquest.com/content/osm/mq_logo.png' border='0'>",
                transitionEffect: "resize",
                wrapDateLine: false,
                isBaseLayer: true
            }
        ));

            layer = new OpenLayers.Layer.WMS(
                "OpenLayers WMS",
                "http://suite.opengeo.org/geoserver/wms?",
                {layers: 'usa:states', transparent: true, format: 'image/png'},
                {singleTile: true, isBaseLayer: false}
            );
            map.addLayer(layer);
            map.zoomToMaxExtent();
            map.addControl( new OpenLayers.Control.LayerSwitcher() );
        }
    </script>
  </head>
  <body onload="init()">
    <h1 id="title"> WMS Untiled Example</h1>

    <div id="tags">
        singletile, tile, light
    </div>
        <p id="shortdesc">
            Shows an example of an "untiled" WMS layer, which requests a single
            image for the entire map view.
        </p>
    <div id="map" class="smallmap"></div>
        <div id="docs">
            An untiled (with singleTile: true) layer will only request a single image at a time.
        </div>
  </body>
</html>
```