Make MV encoding more generic.
Make MV encoding more generic.

This generalizes it to work with an arbtirary number of levels.

This patch only modifies the encoder, which still decode correctly
 in the decoder according to --enable-encoder-check, which is a
 reasonable test that this does not change the bitstream.

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