KdcDecoder::decodeRawInternal(): don't do unsigned integer overflow when calculatinf offset.
KdcDecoder::decodeRawInternal(): don't do unsigned integer overflow when calculatinf offset.

LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed