TIFF: gracefully handle negative origin without asserting in libtiff
TIFF: gracefully handle negative origin without asserting in libtiff

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