matroskamux: fix matroskamux ! matroskademux
Don't carry over DISCONT flags from the input buffers to the output buffer, or the demuxer might reset its state when it receives the first data buffer just after parsing the simple block header, and then expect sane data to follow. Fixes matroskamux ! demux erroring out. https://bugzilla.gnome.org/show_bug.cgi?id=754768 https://bugzilla.gnome.org/show_bug.cgi?id=657805