add smooth drag panning to yahoo layer. the trinity is united. killer props to cr5 for digging through and finding these. ladies and gentlemen, you now have *no*excuse* for not using openlayers. smooth and sexy GYM commercial layers. (Closes #1163)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5230 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

examples/smoothDragging.html

@@ -10,6 +10,7 @@
 
     <script src='http://maps.google.com/maps?file=api&amp;v=2.82&amp;key=ABQIAAAAjpkAC9ePGem0lIq5XcMiuhQtCjFYhdtNUZyqZQW2mFbq_dOIHBSGvjZ-C7_tXAXYdB-ehlOacmC_xA'></script>
     <script src='http://dev.virtualearth.net/mapcontrol/v3/mapcontrol.js'></script>
+    <script src="http://api.maps.yahoo.com/ajaxymap?v=3.0&appid=euzuro-openlayers"></script>
 
     <script src="../lib/OpenLayers.js"></script>
     <script type="text/javascript">
@@ -49,6 +50,12 @@
                 {'type': VEMapStyle.Road, 'sphericalMercator': true}
             ); 
 
+            // create Yahoo layer
+            var yahoo = new OpenLayers.Layer.Yahoo(
+                "Yahoo Street",
+                {'sphericalMercator': true}
+            );
+
             // create WMS layer
             var wms = new OpenLayers.Layer.WMS(
                 "World Map",
@@ -60,7 +67,7 @@
                 }
             );
 
-            map.addLayers([gmap, wms, ve]);
+            map.addLayers([gmap, wms, ve, yahoo]);
             map.addControl(new OpenLayers.Control.LayerSwitcher());
             map.zoomToMaxExtent()
         }

lib/OpenLayers/Layer/Yahoo.js

@@ -92,6 +92,13 @@ OpenLayers.Layer.Yahoo = OpenLayers.Class(
             this.mapObject = new YMap(this.div, this.type, size);
             this.mapObject.disableKeyControls();
             this.mapObject.disableDragMap();
+
+            //can we do smooth panning? (moveByXY is not an API function)
+            if ( !this.mapObject.moveByXY || 
+                 (typeof this.mapObject.moveByXY != "function" ) ) {
+
+                this.dragPanMapObject = null;
+            }                
         } catch(e) {}
     },
 
@@ -248,6 +255,20 @@ OpenLayers.Layer.Yahoo = OpenLayers.Class(
         return this.mapObject.getCenterLatLon();
     },
 
+    /**
+     * APIMethod: dragPanMapObject
+     * 
+     * Parameters:
+     * dX - {Integer}
+     * dY - {Integer}
+     */
+    dragPanMapObject: function(dX, dY) {
+        this.mapObject.moveByXY({
+            'x': -dX,
+            'y': dY
+        });
+    },
+    
     /** 
      * APIMethod: getMapObjectZoom
      *