3 options:
- Mousewheel x -> volume && y -> position
- Mousewheel x -> position && y -> volume
- Mousewheel ignored

See http://forum.videolan.org/viewtopic.php?f=14&t=49194
and #1864.

I think this is not optimal, but it should do it for the VLC 1.0.0-release,
after that, we will see with the multiple-hotkeys development...