Fix toString() override for IE

- All tests once again pass on IE6

lib/class.js

@@ -34,6 +34,23 @@ var util           = require( './util' ),
  */
 var class_meta = {};
 
+/**
+ * IE contains a nasty enumeration "bug" (poor implementation) that makes
+ * toString unenumerable. This means that, if you do obj.toString = foo,
+ * toString will NOT show up in `for` or hasOwnProperty(). This is a problem.
+ *
+ * This test will determine if this poor implementation exists.
+ */
+var enum_bug = (
+        Object.prototype.propertyIsEnumerable.call(
+            { toString: function() {} },
+            'toString'
+        ) === false
+    )
+    ? true
+    : false
+;
+
 
 /**
  * This module may be invoked in order to provide a more natural looking class
@@ -419,6 +436,15 @@ var extend = ( function( extending )
             delete props.__name;
         }
 
+        // IE has problems with toString()
+        if ( enum_bug )
+        {
+            if ( props.toString !== Object.prototype.toString )
+            {
+                props.__toString = props.toString;
+            }
+        }
+
         util.propParse( props, {
             each: function( name, value, keywords )
             {
@@ -567,7 +593,10 @@ var extend = ( function( extending )
                     members[ 'public' ], 'toString'
                 ) ) )
                 {
-                    this.toString = ( cname )
+                    // use __toString if available (see enum_bug), otherwise use
+                    // our own defaults
+                    this.toString = members[ 'public' ].__toString
+                        || ( ( cname )
                             ? function()
                             {
                                 return '[object #<' + cname + '>]';
@@ -576,6 +605,7 @@ var extend = ( function( extending )
                             {
                                 return '[object #<anonymous>]';
                             }
+                        )
                     ;
                 }
             };

test/test-class-extend.js

@@ -292,12 +292,13 @@ for ( var i = 0; i < class_count; i++ )
         result = ''
     ;
 
-    result = Class( 'Foo',
+    result = Class( 'FooToStr',
     {
         toString: function()
         {
             return str;
-        }
+        },
+        bla: function() {},
     })().toString();
 
     assert.equal(