libvlc: restore Teletext functionality
libvlc: restore Teletext functionality

Reverts part of 7db94f4d2fc742537828fbe0c8eb5a and rewrite the code.

chengsun/gtk-npapi-vlc,modulexcite/npapi-vlc,chengsun/gtk-npapi-vlc,rdp/npapi-vlc,modulexcite/npapi-vlc,modulexcite/npapi-vlc,rdp/npapi-vlc,rdp/npapi-vlc,jamesbates/npapi-vlc,jamesbates/npapi-vlc,modulexcite/npapi-vlc,rdp/npapi-vlc,chengsun/gtk-npapi-vlc,jamesbates/npapi-vlc