* modules/audio_filter/channel_mixer/headphone.c, src/libvlc.h:
   moved the headphone-dim config option to the headphone plugin.
* modules/demux/demuxdump.c: the demuxdump-file config optin now has a default value.
* src/libvlc.c: fixed the extraintf config option not to spawn an interface plugin when an invalid name has been given.