API changes, most recent first:
+2017-03-30 - xxxxxxx - lavu 55.53.100 / 55.27.0 - hwcontext.h
+ Add av_hwframe_map() and associated AV_HWFRAME_MAP_* flags.
+ Add av_hwframe_ctx_create_derived().
+
+2017-03-xx - xxxxxxx - lavu 55.52.100 - avutil.h
+ add av_fourcc_make_string() function and av_fourcc2str() macro to replace
+ av_get_codec_tag_string() from lavc.
+
+2017-03-xx - xxxxxxx - lavf 57.68.100 - avformat.h
+ Deprecate that demuxers export the stream rotation angle in AVStream.metadata
+ (via an entry named "rotate"). Use av_stream_get_side_data() with
+ AV_PKT_DATA_DISPLAYMATRIX instead, and read the rotation angle with
+ av_display_rotation_get(). The same is done for muxing. Instead of adding a
+ "rotate" entry to AVStream.metadata, AV_PKT_DATA_DISPLAYMATRIX side data has
+ to be added to the AVStream.
+
2017-03-xx - xxxxxxx - lavc 57.85.101 - avcodec.h
vdpau hardware accelerated decoding now supports the new hwaccel API, which
can create the decoder context and allocate hardware frame automatically.