bpo-29446: tkinter 'import *' only imports what it should (GH-14864)

Add __all__ to tkinter.__init__ and submodules.  Replace 'import *'
with explicit imports in some submodules.
diff --git a/Lib/tkinter/scrolledtext.py b/Lib/tkinter/scrolledtext.py
index 749a06a6..4f9a881 100644
--- a/Lib/tkinter/scrolledtext.py
+++ b/Lib/tkinter/scrolledtext.py
@@ -11,11 +11,11 @@
 Place methods are redirected to the Frame widget however.
 """
 
-__all__ = ['ScrolledText']
-
 from tkinter import Frame, Text, Scrollbar, Pack, Grid, Place
 from tkinter.constants import RIGHT, LEFT, Y, BOTH
 
+__all__ = ['ScrolledText']
+
 
 class ScrolledText(Text):
     def __init__(self, master=None, **kw):