Factor out definitions to a ['child'] so that we could assign the ['attr'] definitions separately.

Also, added AttrDef/EnumTest.php

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@127 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/AttrDef.php

@@ -1,10 +1,12 @@
 <?php
 
+// AttrDef = Attribute Definition
 class HTMLPurifier_AttrDef
 {
-    var $def;
-    function HTMLPurifier_AttrDef($def) {
-        $this->def = $def;
+    function HTMLPurifier_AttrDef() {}
+    
+    function validate() {
+        trigger_error('Cannot call abstract function', E_USER_ERROR);
     }
 }