Allow DNG files to ignore byte count via hint.
Allow DNG files to ignore byte count via hint.

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