Preserve original ce_flags when registering class

Bug that regularly sneaks in: ZEND_ACC_FINAL is set before calling
zend_register_internal_class() and promptly gets ignored. Remove
this footgun by preserving flags from the original CE.

Author: nikic

Zend/zend_API.c

@@ -2577,7 +2577,7 @@ static zend_class_entry *do_register_internal_class(zend_class_entry *orig_class
 
 	class_entry->type = ZEND_INTERNAL_CLASS;
 	zend_initialize_class_data(class_entry, 0);
-	class_entry->ce_flags = ce_flags | ZEND_ACC_CONSTANTS_UPDATED | ZEND_ACC_LINKED | ZEND_ACC_RESOLVED_PARENT | ZEND_ACC_RESOLVED_INTERFACES;
+	class_entry->ce_flags = orig_class_entry->ce_flags | ce_flags | ZEND_ACC_CONSTANTS_UPDATED | ZEND_ACC_LINKED | ZEND_ACC_RESOLVED_PARENT | ZEND_ACC_RESOLVED_INTERFACES;
 	class_entry->info.internal.module = EG(current_module);
 
 	if (class_entry->info.internal.builtin_functions) {

ext/reflection/tests/ReflectionAttribute_final.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Check that ReflectionAttribute is final
+--FILE--
+<?php
+
+class T extends ReflectionAttribute {}
+
+?>
+--EXPECTF--
+Fatal error: Class T may not inherit from final class (ReflectionAttribute) in %s on line %d