python: tkvlc.py updates. (#99)
python: tkvlc.py updates. (#99)

The tkvlc.py example works and looks a lot better now on macOS.  The menu items and shortcut keys all work like proper macOS applications and compensate for the buttons hidden under the video.

The Play menu, button and shortcut key now toggle between Play and Pause, the Mute menu, button and shortcut key toggles between Mute and Unmute.

The Quit menu, the Q- and W-shortcut keys and the error dialog are all working properly now.

The Full Screen menu and shortcut behaves like other macOS applications, including the Escape key.

The timer class has been replaced by a one-line call to Tk's after method.

Unresolved remain 2 issues:

- The buttons and sliders in the main window are overwritten by the video. The buttons do work when clicking near the bottom of the video.

- Stopping the video from Play or Pause results in an error message fro libVLC:
```
        # [h264 @ 0x7f84fb061200] get_buffer() failed
        # [h264 @ 0x7f84fb061200] thread_get_buffer() failed
        # [h264 @ 0x7f84fb061200] decode_slice_header error
        # [h264 @ 0x7f84fb061200] no frame!
```
Like before, only tested on macOS 10.13.6 with Tk 8.6.9 and vlc.py 3.0.6109 using Python 3.7.4 64-bit. If you have a Windows and/or *nix system with Python 3.4+ , please run this tkvlc.py.

Some screen shots follow.
oaubert/python-vlc,oaubert/python-vlc