Fix EXT_INTER unit test failure in 32-bit builds
Fix EXT_INTER unit test failure in 32-bit builds

Align new buffers that are used in interintra and wedgeinterinter prediction.
BUG=https://bugs.chromium.org/p/webm/issues/detail?id=1196

Change-Id: I1ef49fdf13c79a22cf8a1737e3d3052da0a92dfe

luctrudeau/aom,smarter/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,smarter/aom,mbebenita/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom