Rockbox

This is a simple change to streamline the user interface in party mode.

The play/pause button was suppressed and unused in party mode. The current playlist was accessible in party mode by walking through the main menu. And it was possible to return to the wps with a few more button presses.

Now one can directly jump to current playlist with a press of the play/pause button. A second press of the play/pause button returns one to the wps. The ability to easily jump between the wps and the current playlist was a sorely missed feature that was present in the original software of my Sansa e200. This at least partially addresses this issue. Open patches  FS#5555  and FS#5886 also address this issue in a different way.

This is my first patch and while it is ridiculously simple it did bring up a couple questions which I left as comments in the source. I'd appreciate someone with experience reviewing this patch and making suggestions to assist me in putting this in final form to hopefully be integrated.