Issue #15576: Allow extension modules to be a package's __init__
module again. Also took the opportunity to stop accidentally exporting
_imp.extension_suffixes() as public.
diff --git a/Lib/importlib/machinery.py b/Lib/importlib/machinery.py
index fed6f2c..ff826e4 100644
--- a/Lib/importlib/machinery.py
+++ b/Lib/importlib/machinery.py
@@ -3,7 +3,8 @@
 import _imp
 
 from ._bootstrap import (SOURCE_SUFFIXES, DEBUG_BYTECODE_SUFFIXES,
-                         OPTIMIZED_BYTECODE_SUFFIXES, BYTECODE_SUFFIXES)
+                         OPTIMIZED_BYTECODE_SUFFIXES, BYTECODE_SUFFIXES,
+                         EXTENSION_SUFFIXES)
 from ._bootstrap import BuiltinImporter
 from ._bootstrap import FrozenImporter
 from ._bootstrap import WindowsRegistryFinder
@@ -13,7 +14,6 @@
 from ._bootstrap import SourcelessFileLoader
 from ._bootstrap import ExtensionFileLoader
 
-EXTENSION_SUFFIXES = _imp.extension_suffixes()
 
 def all_suffixes():
     """Returns a list of all recognized module suffixes for this process"""