Fix non-pow2 tiles for accum_sample_closest (previously done for other modes)
Fix non-pow2 tiles for accum_sample_closest (previously done for other modes)

YangYangTL/oiio,mcanthony/oiio,lgritz/oiio,scott-wilson/oiio,sambler/oiio,OpenImageIO/oiio,cwilling/oiio,OpenImageIO/oiio,sambler/oiio,YangYangTL/oiio,micler/oiio,micler/oiio,scott-wilson/oiio,mcanthony/oiio,lgritz/oiio,sambler/oiio,mcanthony/oiio,cwilling/oiio,bdeluca/oiio,lgritz/oiio,YangYangTL/oiio,cwilling/oiio,scott-wilson/oiio,lgritz/oiio,scott-wilson/oiio,mcanthony/oiio,OpenImageIO/oiio,sambler/oiio,bdeluca/oiio,bdeluca/oiio,bdeluca/oiio,cwilling/oiio,YangYangTL/oiio,micler/oiio,micler/oiio,OpenImageIO/oiio