API changes, most recent first:
+2021-04-27 - xxxxxxxxxx - lavc yyyyyyyyy - avcodec.h
+ Constified AVCodecParserContext.parser.
+
2021-04-27 - xxxxxxxxxx - lavd yyyyyyyyy - avdevice.h
The av_*_device_next API functions now accept and return
pointers to const AVInputFormat resp. AVOutputFormat.