MacOSX: detect the architectures supported by Tk.framework and build _tkinter only for those architectures.
MacOSX: detect the architectures supported by
Tk.framework and build _tkinter only for those
architectures.

This replaces the hardcoded solution that is no
longer valid now that 64-bit capable versions of
Tk are available on OSX.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator