Add extension management to __all__.
diff --git a/Lib/copy_reg.py b/Lib/copy_reg.py
index 1276564..cf801cb 100644
--- a/Lib/copy_reg.py
+++ b/Lib/copy_reg.py
@@ -6,7 +6,8 @@
 
 from types import ClassType as _ClassType
 
-__all__ = ["pickle","constructor"]
+__all__ = ["pickle", "constructor",
+           "add_extension", "remove_extension", "clear_extension_cache"]
 
 dispatch_table = {}
 safe_constructors = {}