I don't quite understand this, but I think I should.  Here are preliminary questions.

0.  It seems that this pushes conversions from python code (app.py, tkinter.py) to C (_tkinter.py).  Correct?  What is being gained from a user viewpoint?

1. "getint, getdouble and getboolean were thin wrappers around Tcl functions that converted string result of Tcl call to specified Python type."

How does this match getint and getdouble being synonyms for builtins?
-    getint = int
-    getdouble = float
Or were 'int' and 'float' overriden before this?

2. Does the change break existing code?  In particular, is the idlelib change necessary or optional?

3. Should there be a doc change, at least in docstrings?