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

[vbkhp@…]

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.

This breaks the py27-matplotlib build which parses version and expects a number:

see ​https://github.com/matplotlib/matplotlib/commit/04b4e5091978 on how to fix it.

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

[jmroot (Joshua Root)]

Please remember to fill in the Port field and cc the maintainers.