Dav1d for OS/2

Changes for 1.5.1 'Sonic': -------------------------- 1.5.1 is a minor release of dav1d, focusing on optimizations and stack reduction: - Rewrite of the looprestoration (SGR, wiener) to reduce stack usage - Rewrite of {put,prep}_scaled functions Now, the required stack space for dav1d should be: 62 KB on x86_64 and 58KB on arm and aarch64. - Improvements on the SSSE3 SGR - Improvements on ARM32/ARM64 looprestoration optimizations - RISC-V: blend optimizations for high bitdepth - Power9: blend optimizations for 8bpc - Port RISC-V to POSIX/non-Linux OS - AArch64: Add Neon implementation of load_tmvs - Fix a rare, but possible deadlock, in flush() Changes for 1.5.0 'Sonic': -------------------------- 1.5.0 is a major release of dav1d, that: - WARNING: we removed some of the SSE2 optimizations, so if you care about systems without SSSE3, you should be careful when updating! - Add Arm OpenBSD run-time CPU feature - Optimize index offset calculations for decode_coefs - picture: copy HDR10+ and T35 metadata only to visible frames - SSSE3 new optimizations for 6-tap (8bit and hbd) - AArch64/SVE: Add HBD subpel filters using 128-bit SVE2 - AArch64: Add USMMLA implempentation for 6-tap H/HV - AArch64: Optimize Armv8.0 NEON for HBD horizontal filters and 6-tap filters - Power9: Optimized ITX till 16x4. - Loongarch: numerous optimizations - RISC-V optimizations for pal, cdef_filter, ipred, mc_blend, mc_bdir, itx - Allow playing videos in full-screen mode in dav1dplay