* changes:
Make gop size independent from kf_zeromotion_pct
Add get_frames_to_next_key()
Rename i by frames_to_key in find_next_key_frame
Remove input_stats when decide frames_to_key
Remove twopass param from test_candidate_kf
Pass first_pass_info/show_idx to test_candidate_kf
Refactor test_candidate_kf()
Decide the key frame directly when auto_key is off
Remove detect_transition_to_still()
Change the interface of find_next_key_frame