tifflike: Heuristically add high-order bits of NDPI value offsets
tifflike: Heuristically add high-order bits of NDPI value offsets

NDPI value offsets are 32-bit fields but hold 64-bit offsets; the high-
order bits are implied.  Try to guess them.

openslide/openslide,openslide/openslide,openslide/openslide,openslide/openslide