Add an option for turning off smooth dragging, since it works on a pixel level,

and our geography doesn't, so the numbers end up off in the north-south
direction when *not* using spherical mercator. Now, if someone comes to use us
and says 'oh my! you ruined me!' we can say 'options! we love options!' and do
a rain dance. (Closes #1164) 


git-svn-id: http://svn.openlayers.org/trunk/openlayers@5229 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/EventPane.js

@@ -15,6 +15,18 @@
  *  - <OpenLayers.Layer>
  */
 OpenLayers.Layer.EventPane = OpenLayers.Class(OpenLayers.Layer, {
+    
+    /**
+     * APIProperty: smoothDragPan
+     * {Boolean} smoothDragPan determines whether non-public/internal API
+     * methods are used for better performance while dragging EventPane layers.
+     * When not in sphericalMercator mode, the smoother dragging doesn't
+     * actually move north/south directly with the number of pixels moved,
+     * resulting in a slight offset when you drag your mouse north south with
+     * this option on. If this visual disparity bothers you, you should turn 
+     * this option off, or use spherical mercator. Default is on.
+     */
+    smootherDragging: true,
 
     /**
      * Property: isBaseLayer
@@ -226,7 +238,8 @@ OpenLayers.Layer.EventPane = OpenLayers.Class(OpenLayers.Layer, {
 
                     var center = this.getMapObjectLonLatFromOLLonLat(newCenter);
 
-                    if (dragging && this.dragPanMapObject) {
+                    if (dragging && this.dragPanMapObject && 
+                        this.smoothDragPan) {
                         var resolution = this.map.getResolution();
                         var dX = (newCenter.lon - oldCenter.lon) / resolution;
                         var dY = (newCenter.lat - oldCenter.lat) / resolution;