Increase global motion translation precision
Increase global motion translation precision

increases the translational part of global motion models
to the same 1/64 pel precision which is used by the warp filter.

Change-Id: I7267b18b123662416bc5c8095186b6a5eef2f7f1

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