ytdl_hook: use no_clip for separate audio streams

I noticed that some ytdl streams have a start time other than 0. There's
currently no mechanism inside of the EDL stuff that determines this
start time correctly, so it can happen that if the start time is high,
demux_timeline.c tries to clip off the entire video and audio, resulting
in failure of playback.

As a counter measure, use the no_clip header, which entirely disables
clipping against time ranges in demux_timeline.c. (It's basically a
hack.)

player/lua/ytdl_hook.lua

@@ -331,7 +331,7 @@ local function add_single_video(json)
         if #streams > 1 then
             -- merge them via EDL
             for i = 1, #streams do
-                streams[i] = edl_escape(streams[i])
+                streams[i] = "!no_clip;" .. edl_escape(streams[i])
             end
             streamurl = "edl://!no_chapters;" ..
                         table.concat(streams, ";!new_stream;") .. ";"