hotkeys: new hotkey for toggling subtitles

A subtitle track chosen by hotkey "v" is remembered in variable "spu-choice".
The hotkey "Shift+v" toggles subtitle visibility.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
Contribs: Update libbluray to 0.6.0

And activate BD-J
Update live555 Contribs