Updates for libavformat version 59

[iwakuraSSBM]

Add preprocessor checks for LIBAVFORMAT_VERSION_MAJOR to fix changes in version 59:

• AVFormatContext::filename deprecated
• av_guess_format() now returns const AVOutputFormat*
• av_register_all() deprecated

[iwakuraSSBM]

Don't know if this a double request, I thought I had made the request already but it disappeared?

[iwakuraSSBM]

For reference it appears as though the av_register_all function has been completely removed and no functionality replaces it. https://github.com/leandromoreira/ffmpeg-libav-tutorial/issues/29

[Tinob]

looks good