improve or remove parsing of Tkinter.__version__ required for newer python versions

[juliantaylor]

due to the cpython hg transition the version attribute of tkinter has been removed in python 3 and in the python 2.7 rc1 it does not contain a number anymore.
see http://bugs.python.org/issue12236
http://hg.python.org/cpython/file/f3553d5083f8/Lib/tkinter/__init__.py

This breaks the matplotlib build which parses version and expects a number:

OPTIONAL BACKEND DEPENDENCIES
                libpng: 1.2.44
Traceback (most recent call last):
  File "./setup.py", line 162, in <module>
    if check_for_tk() or (options['build_tkagg'] is True):
  File "/build/buildd/matplotlib-1.0.1/setupext.py", line 832, in check_for_tk
    (Tkinter.__version__.split()[-2], Tkinter.TkVersion, Tkinter.TclVersion))
IndexError: list index out of range

[ddale]

This issue was already addressed in commit 04b4e50 on v1.0.x-maint and 9bcca38 on master. Thank you for the report.

[efiring]

Those commits don't take care of version being missing in py3k. Since master is periodically merged into py3k, I am inclined to fix master to handle the missing version case along with everything else.

[ddale]

My mistake, thanks for catching.

[efiring]

Fixed in master with e4a34df