python2/python3.macros

New Python2/Python3 macros for future mga6:

- %{py_ver}, %{py2_ver}, %{py2ver}, %{pyver} should be:           %{python2_version}

- %{py3_ver} %{py3ver} should be:                                 %{python3_version}

- %{py_platsitedir}, %{python_sitearch} should be:                %{python2_sitearch}

- %{py3_platsitedir} should be:                                   %{python3_sitearch}

- %{py_sitedir}, %{py_puresitedir}, %{python_sitelib} should be:  %{python2_sitelib}

- %{py3_puresitedir} should be:                                   %{python3_sitelib}

- %{__python} should be:                                          %{__python2}