Thanks, Michael. I'll try to push this upsteam myself (I wonder this bug caused so much discussions).
I'd like to perform a quick poll there: "Should the play queue be sortable in the such way?"
First off it is a "queue" so it is doesn't intend it's elements can be reordered. My patch obeys this logic for now.
But, if I'd make the clickable headers for it, this feature doesn't obstruct users who do not use it. If you want to use it - you can.
So, the current solution looks like a dumb restriction for me. Please, help me to decide which way is the best.