[DONE] Auto-ISO: 1/4000 please...

[Marsu42]

When doing high speed action shots Auto-ISO only reaching 1/2000 is a bit limiting - imho it'd be nice to add 1/4000 to the list for cameras that have 1/8000 shutter (afaik everything except Rebels & 6d).

EDIT: I just added it myself and will post a pull request - though my solution is static (different #define for different cameras in features.h) rather than dynamic though FASTEST_SHUTTER_SPEED_RAW