API changes, most recent first:
+2017-xx-xx - xxxxxxx - lavr 4.0.0 - avresample.h
+ Deprecate the entire library. Merged years ago to provide compatibility
+ with Libav, it remained unmaintained by the FFmpeg project and duplicated
+ functionality provided by libswresample.
+
+ In order to improve consistency and reduce attack surface, it has been deprecated.
+ Users of this library are asked to migrate to libswresample, which, as well as
+ providing more functionality, is faster and has higher accuracy.
+
2017-xx-xx - xxxxxxx - lavc 58.9.100 - avcodec.h
Deprecate av_lockmgr_register(). You need to build FFmpeg with threading
support enabled to get basic thread-safety (which is the default build