[BT] Code style fix.
[BT] Removed QT_VERSION check.

We don't support Qt 4.7 and older after all.
[BT] Basic AddMagnetDialog for #1631.
[BT] Style fixes.
[LMP HS] Set playing state on first connect (and revert on disconnect).
[LMP HS] Create pad only when state is PLAYING.
[LMP HS] Add sockets only in PLAYING state.