tighten DNG opcode bounds checks
tighten DNG opcode bounds checks

LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,klauspost/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,anarsoul/rawspeed,anarsoul/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,anarsoul/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,klauspost/rawspeed,LebedevRI/rawspeed