make _.initWrapper() that builds the wrapper prototye

The intention is that underscore Consumers MUST call _.initWrapper()
in their code to allow the OO style usage, or a runtime error is thrown.
This would break backwards compatability, so for the moment I call
initWrapper myself at the end of underscore.

However, if I comment out my call to initWrapper and don't call it
in user code, then the compiler can strip an empty underscore with
no user code from 2137 -> 100 bytes.  Making the user explicitly say
they want OO wrapping is the only way to achieve this, otherwise the
compiler will always keep the OO wrapper code around.

underscore.js

@@ -43,7 +43,7 @@
     native_keys         = Object['keys'];
 
   // Create a safe reference to the Underscore object for reference below.
-  var _ = function(obj) { return new wrapper(obj); };
+  var _ = function(obj) { return _.buildWrapper(obj) };
 
   // Export the Underscore object for CommonJS.
   if (typeof exports !== 'undefined') exports._ = _;
@@ -68,8 +68,11 @@
       } else if (_.isNumber(obj.length)) {
         for (var i=0, l=obj.length; i<l; i++) iterator.call(context, obj[i], i, obj);
       } else {
-        var keys = _.keys(obj), l = keys.length;
-        for (var i=0; i<l; i++) iterator.call(context, obj[keys[i]], keys[i], obj);
+        for (var key in obj) 
+          if (hasOwnProperty.call(obj, key)) 
+            iterator.call(context, obj[key], key, obj);
+        // var keys = _.keys(obj), l = keys.length;
+        // for (var i=0; i<l; i++) iterator.call(context, obj[keys[i]], keys[i], obj);
       }
     } catch(e) {
       if (e != breaker) throw e;
@@ -639,53 +642,60 @@
   _.methods  = _.functions;
 
   // ------------------------ Setup the OOP Wrapper: --------------------------
-
-  // If Underscore is called as a function, it returns a wrapped object that
-  // can be used OO-style. This wrapper holds altered versions of all the
-  // underscore functions. Wrapped objects may be chained.
-  var wrapper = function(obj) { this._wrapped = obj; };
+  _.buildWrapper = function () { throw "Call _.initWrapper() to enable OO wrapping" }
 
-  // Helper function to continue chaining intermediate results.
-  var result = function(obj, chain) {
-    return chain ? _(obj).chain() : obj;
-  };
-
-  // Add all of the Underscore functions to the wrapper object.
-  each(_.functions(_), function(name) {
-    var method = _[name];
-    wrapper.prototype[name] = function() {
-      var args = _.toArray(arguments);
-      unshift.call(args, this._wrapped);
-      return result(method.apply(_, args), this._chain);
-    };
-  });
-
-  // Add all mutator Array functions to the wrapper.
-  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
-    var method = Array_Prototype[name];
-    wrapper.prototype[name] = function() {
-      method.apply(this._wrapped, arguments);
-      return result(this._wrapped, this._chain);
+  _.initWrapper = function () {
+    // If Underscore is called as a function, it returns a wrapped object that
+    // can be used OO-style. This wrapper holds altered versions of all the
+    // underscore functions. Wrapped objects may be chained.
+    var wrapper = function(obj) { this._wrapped = obj; };
+
+    // Overwrite method called from _()
+    _.buildWrapper = function (obj) { return new wrapper(obj) };
+
+    // Helper function to continue chaining intermediate results.
+    var result = function(obj, chain) {
+      return chain ? _(obj).chain() : obj;
     };
-  });
 
-  // Add all accessor Array functions to the wrapper.
-  each(['concat', 'join', 'slice'], function(name) {
-    var method = Array_Prototype[name];
-    wrapper.prototype[name] = function() {
-      return result(method.apply(this._wrapped, arguments), this._chain);
-    };
-  });
+    // Add all of the Underscore functions to the wrapper object.
+    each(_.functions(_), function(name) {
+      var method = _[name];
+      wrapper.prototype[name] = function() {
+        var args = _.toArray(arguments);
+        unshift.call(args, this._wrapped);
+        return result(method.apply(_, args), this._chain);
+      };
+    });
 
-  // Start chaining a wrapped Underscore object.
-  wrapper.prototype.chain = function() {
-    this._chain = true;
-    return this;
-  };
+    // Add all mutator Array functions to the wrapper.
+    each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
+      var method = Array_Prototype[name];
+      wrapper.prototype[name] = function() {
+        method.apply(this._wrapped, arguments);
+        return result(this._wrapped, this._chain);
+      };
+    });
 
-  // Extracts the result from a wrapped and chained object.
-  wrapper.prototype.value = function() {
-    return this._wrapped;
-  };
+    // Add all accessor Array functions to the wrapper.
+    each(['concat', 'join', 'slice'], function(name) {
+      var method = Array_Prototype[name];
+      wrapper.prototype[name] = function() {
+        return result(method.apply(this._wrapped, arguments), this._chain);
+      };
+    });
 
+    // Start chaining a wrapped Underscore object.
+    wrapper.prototype.chain = function() {
+      this._chain = true;
+      return this;
+    };
+
+    // Extracts the result from a wrapped and chained object.
+    wrapper.prototype.value = function() {
+      return this._wrapped;
+    };
+  }
+
+  _.initWrapper();
 })();