M-JPEG: fix MJPEG demux to be able to read VLC MPJPEG streams
M-JPEG: fix MJPEG demux to be able to read VLC MPJPEG streams

That's clearly a hack but at least it works.

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