Log Message:
dav1d: update to 1.4.2.

Changes for 1.4.2 'Road Runner':
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1.4.2 is a small release of dav1d, improving notably ARM, AVX-512 and PowerPC
 - AVX2 optimizations for 8-tap and new variants for 6-tap
 - AVX-512 optimizations for 8-tap and new variants for 6-tap
 - Improve entropy decoding on ARM64
 - New ARM64 optimizations for convolutions based on DotProd extension
 - New ARM64 optimizations for convolutions based on i8mm extension
 - New ARM64 optimizations for subpel and prep filters for i8mm
 - Misc improvements on existing ARM64 optimizations, notably for put/prep
 - New PowerPC9 optimizations for loopfilter
 - Support for macOS kperf API for benchmarking

Changes for 1.4.1 'Road Runner':
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1.4.1 is a small release of dav1d, improving notably ARM and RISC-V speed

- Optimizations for 6tap filters for NEON (ARM)
- More RISC-V optimizations for itx (4x8, 8x4, 4x16, 16x4, 8x16, 16x8)
- Reduction of binary size on ARM64, ARM32 and RISC-V
- Fix out-of-bounds read in 8bpc SSE2/SSSE3 wiener_filter
- Msac optimizations