Confusingly, BKE_scene_frame_get did not match the frame number as expected by
BKE_scene_frame_set. Instead it return the value after time remapping, which
is commonly named "ctime".
* Rename BKE_scene_frame_get to BKE_scene_ctime_get
* Add a new BKE_scene_frame_get that matches BKE_scene_frame_set
* Use int/float depending if fractional frame is expected