demux: hls: prevent duration/starttime rounding errors
demux: hls: prevent duration/starttime rounding errors

Some streams have microsecond durations, > default timescale

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc