Display the title length (when known) in Playback->Title/Navigation.
Display the title length (when known) in Playback->Title/Navigation.

It closes #4021 at the core level. The access_demux/demux need to set
input_title_t::i_length to actually change something.

shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,krichter722/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.2,krichter722/vlc,krichter722/vlc,jomanmuk/vlc-2.2,krichter722/vlc