Fixes an overflow in od_compute_var_4x4() when the prefilter creates large values
Fixes an overflow in od_compute_var_4x4() when the prefilter creates large values

Negligible impact on metrics. Also tried rounding, but it didn't help (slightly worse, but in the noise)

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