Because onselectstart is null by default, our logic to set it and

replace it was somewhat lacking. This changes the behavior such that 
using hte drag handler does not totally disable text selection in IE. 
Patch from Bart, r=me (Closes #906)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@5911 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Handler/Drag.js

@@ -167,7 +167,7 @@ OpenLayers.Handler.Drag = OpenLayers.Class(OpenLayers.Handler, {
             OpenLayers.Event.stop(evt);
             
             if(!this.oldOnselectstart) {
-                this.oldOnselectstart = document.onselectstart;
+                this.oldOnselectstart = (document.onselectstart) ? document.onselectstart : function() { return true; };
                 document.onselectstart = function() {return false;};
             }