Adds SIMD support for blending 32x32 blocks.
Adds SIMD support for blending 32x32 blocks.

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