Rockbox

When moving a track within a playlist to any position before the currently playing track, the index of the currently playing track on the playlist gets shifted back by 1. This causes two problems:

-The playlist shows a wrong track as the current track being played
-The currently playing track is played once more when finished

The only exception is when moving to the first position in the playlist, since that is handled as a prepend and works as expected.

AFAIK this issue affects all players and has been present at least since 3.6 (see #FS11376 http://www.rockbox.org/tracker/task/11376)

Attached is a patch against 49bcf35 that (hopefully) fixes this issue by comparing the display indexes of the positions we're moving from/to and the currently playing track, incrementing the playlist index when neccessary.