Add support for mono output to dump_video.c.
Add support for mono output to dump_video.c.

ascent12/daala,kodabb/daala,mbebenita/daala,nvoron23/daala,ascent12/daala,kustom666/daala,kodabb/daala,KyleSiefring/daala,xiph/daala,jmvalin/daala,felipebetancur/daala,KyleSiefring/daala,tribouille/daala,KyleSiefring/daala,mbebenita/daala,HeadhunterXamd/daala,xiph/daala,luctrudeau/daala,felipebetancur/daala,KyleSiefring/daala,nvoron23/daala,tribouille/daala,kodabb/daala,ycho/daala,ycho/daala,nvoron23/daala,ycho/daala,xiph/daala,jmvalin/daala,mbebenita/daala,xiph/daala,luctrudeau/daala,xiph/daala,xiphmont/daala,mbebenita/daala,HeadhunterXamd/daala,HeadhunterXamd/daala,luctrudeau/daala,kustom666/daala,kustom666/daala,kustom666/daala,felipebetancur/daala,ycho/daala,jmvalin/daala,jmvalin/daala,xiphmont/daala,luctrudeau/daala,HeadhunterXamd/daala,kustom666/daala,xiphmont/daala,xiphmont/daala,nvoron23/daala,ascent12/daala,tribouille/daala,KyleSiefring/daala,mbebenita/daala,felipebetancur/daala,HeadhunterXamd/daala,tribouille/daala,nvoron23/daala,jmvalin/daala,luctrudeau/daala,kodabb/daala,kodabb/daala,ascent12/daala,xiphmont/daala,ycho/daala,felipebetancur/daala,tribouille/daala,ascent12/daala