add os.reload_environ to __all__

Author: guoci

Lib/os.py

@@ -832,6 +832,7 @@ def reload_environ():
         env_data.clear()
         env_data.update(data)
 
+    __all__.append("reload_environ")
 
 def getenv(key, default=None):
     """Get an environment variable, return None if it doesn't exist.