I've talked with Brett and we agreed on a plan slightly different from
the one described in PEP 3108, which seems to be better for tkinter.

The first step would be creating a tkinter package and then moving each
file in lib-tk to this new directory, correcting imports and the case
and renaming Tkinter.py to __init__.py so the directory is marked as a
package.

After this step I can proceed with more patches, including stub modules,
tests in test_py3kwarn and continue with the rest of the plan.

I'm attaching two files I've used to do this first step. One is a .py
file, which will do the proper renamings and then there is a patch which
should be applied to fix imports inside the tkinter package.