macosx: video effects: add brightness-threshold to the profiles string
macosx: video effects: add brightness-threshold to the profiles string

This is done in a backward-compatible manner: Once an existing profile is saved,
the new format is used.

Opening the new format with an old VLC version will work, too, but you will
lose changes from the new format.

refs #11643

vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,krichter722/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,krichter722/vlc,xkfz007/vlc,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,krichter722/vlc,xkfz007/vlc