Don't enqueue file if it's already enqueued

[Brent2121]

I swear I've seen this option buried somewhere in the winamp settings pages, but I can't find it anywhere, so if it already exists, thank you to the winamp devs and I apologize for wasting your time.

I'd like an option that would make it so that if I try to add a song to the active playlist, it won't be added if it's already on there. Essentially what the "live playlist duplicate remover" plugin does (although it somehow only seems to remove a fraction of the duplicates). But instead of using a constantly running thread or timer like that plugin appears to do, I think it'd be easier and more efficient if the new feature simply verifies that a song isn't in the playlist before adding it.