* Correct use of deprecated parameters

codec_context_->rc_buffer_aggressivity marked as "currently useless", so removed
codec_context_->frame_skip_threshold access through new priv_data api

* New names for pixel formats

* AVPicture is deprecated, use AVFrame

* Switch to non-deprecated free functions

* Use new encoding api for newer versions

encode_video2 is deprecated

* codec_context is deprecated, use packet flags