fixes for tkinter in nltk.app and nltk.draw packages

In the nltk.app and nltk.draw packages, updated modules that use tkinter by running 2to3.py. Manually fixed some spots that 2to3.py missed.

To ensure backward compatibility with python2.6, updated
- nltk/compat.py to add an import hook (PEP 302) for tkinter
- nltk/util.py to update in_idle function which was broken for py3