[1.7.0] Implement HTMLDefinition cache (very hacked together, but long unit test times were driving me crazy!)

- Add extra protection in AttrDef_URI against phantom Schemes
- Doctype moved from config to HTMLDefinition
- AttrDef_URITest mocks have more generic object parameters to deal with PHP4's copy-happy behavior

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1089 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/AttrDef/URI.php

@@ -158,6 +158,14 @@ class HTMLPurifier_AttrDef_URI extends HTMLPurifier_AttrDef
             );
         }
         
+        // something funky weird happened in the registry, abort!
+        if (!$scheme_obj) {
+            trigger_error(
+                'Default scheme object "' . $config->get('URI', 'DefaultScheme') . '" was not readable',
+                E_USER_WARNING
+            );
+            return false;
+        }
         
         // the URI we're processing embeds_resource a resource in the page, but the URI
         // it references cannot be located