#661 Allow playlist window to appear in Windows Alt-Tab list

[Dave Ney]

When the user allows the SMPLayer playlist to be visible (View > Playlist), allow the resulting playlist window to appear in the Windows Alt-Tab list so that it can be navigated to and its contents manipulated by keyboard.

[Ricardo Villalba]

I'd like to, but many people like the playlist to be dockable into the main window and if I convert the playlist in a real window then it won't be dockable anymore.