v2.2.29 (20211116)
- floating point number formats are local independent again. Regression since 2.2.27
- mt_merge accept "top_left" chroma placement ("topleft" is still valid)
- (avx2: stop using _mm256_zeroupper - compilers are do that automatically,
mainly because LLVM (12.0) generated suboptimal save-restore-all-xmm registers in
prologue and epilogue when encountered with it.)