n5.1.9
libavutil: Detect MMI and MSA flags for MIPS
libavcodec/mips: Fix build errors reported by clang
mips: add support for R6
mips: Fix potential illegal instruction error.
avutil/mips/intreadwrite: build fix for mips64r6 (instruction 'lwl' not supported)
Include attributes.h directly
avutil/mips: Use $at as MMI macro temporary register