Our build of qt, which is based on Valve's build of qt. We'll try to keep a list of changes below, but really if you're trying to use this you're on your own.
- QDockWidget should always show a tab when docked
- QDockWidget can be dragged with its tab
- QDockWidget shows close buttons on tabs (if closable)
- QDockWidget titlebar is never shown (and is removed)