Correcting the callback for the script protocol.

In f08119b, the default syntax for the script protocol's callback made it so the callbacks looked like `OpenLayers.Protocol.Script.registry[c1]`.  This essentially breaks the script protocol everywhere except where `c1` is defined and equals "c1" (the string).

Tests with this change demonstrate that default callbacks will now look like `OpenLayers.Protocol.Script.registry['c1']` (properly accessing the `c1` property of the registry object).

lib/OpenLayers/Protocol/Script.js

@@ -57,9 +57,9 @@ OpenLayers.Protocol.Script = OpenLayers.Class(OpenLayers.Protocol, {
      * APIProperty: callbackTemplate
      * {String} Template for creating a unique callback function name
      * for the registry. Should include ${id}.
-     * Default is "OpenLayers.Protocol.Script.registry[${id}]".
+     * Default is "OpenLayers.Protocol.Script.registry['${id}']".
      */
-    callbackTemplate: "OpenLayers.Protocol.Script.registry[${id}]",
+    callbackTemplate: "OpenLayers.Protocol.Script.registry['${id}']",
 
     /**
      * APIProperty: callbackKey

tests/Protocol/Script.html

@@ -135,7 +135,7 @@
     }
 
     function test_createRequest(t) {
-        t.plan(4);
+        t.plan(5);
         var protocol = new OpenLayers.Protocol.Script({
             callbackKey: 'cb_key',
             callbackPrefix: 'cb_prefix:'
@@ -150,8 +150,11 @@
 
         t.eq(script.type, 'text/javascript',
             'created script has a correct type');
-        t.eq(script.src, 'http://bar_url/?k=bar_param&cb_key=cb_prefix%3AOpenLayers.Protocol.Script.registry%5Bbar%5D',
-            'created script has a correct url');
+
+        var params = OpenLayers.Util.getParameters(script.src);        
+        t.eq(params.k, "bar_param", "custom query string param");
+        t.eq(params.cb_key, "cb_prefix:OpenLayers.Protocol.Script.registry['bar']", "callback with prefix");
+
         t.eq(script.id, 'OpenLayers_Protocol_Script_bar',
             'created script has a correct id');