[1.7.0] Add native support for required elements

- Factored out large portion of ValidateAttributes to AttrValidator
- Implemented ValidateAttributes armor
- Fix clear cache bug
- Implement armoring for ValidateAttributes

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1174 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/ElementDef.php

@@ -85,6 +85,13 @@ class HTMLPurifier_ElementDef
      */
     var $descendants_are_inline = false;
     
+    /**
+     * List of the names of required attributes this element has. Dynamically
+     * populated.
+     * @public
+     */
+    var $required_attr = array();
+    
     /**
      * Lookup table of tags excluded from all descendants of this tag.
      * @note SGML permits exclusions for all descendants, but this is
@@ -174,6 +181,13 @@ class HTMLPurifier_ElementDef
         }
     }
     
+    /**
+     * Retrieves a copy of the element definition
+     */
+    function copy() {
+        return unserialize(serialize($this));
+    }
+    
 }
 
 ?>