add indexOf() function to array - returns first index of a given element in an array. useful for testing, etc

git-svn-id: http://svn.openlayers.org/trunk/openlayers@225 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Util.js

@@ -519,7 +519,22 @@ Array.prototype.clear = function() {
     this.length = 0;
 };
 
-
+/**
+* @param {Object} element
+*
+* @returns The first index of the element in the array if found. Else returns -1
+* @type int
+*/
+Array.prototype.indexOf = function(element) {
+    var index = -1;
+    for(var i=0; i < this.length; i++) {
+        if (this[i] == element) {
+            index = i;
+            break;
+        }
+    }
+    return index;    
+}
 
 /** 
 * zIndex is NOT set