changes in sbcl-2.2.6 relative to sbcl-2.2.5: * minor incompatible change: support for 32-bit x86 on macOS has been removed. * new contrib: sb-simd, to provide a convenient interface for SIMD programming on x86-64. (Thanks to Marco Heisig and other sb-simd contributors) * enhancement: core compression now uses zstd instead of zlib. (lp#1881089) * enhancement: provide compiler warnings for specialized array type mismatches in CONCATENATE. * enhancement: provide compiler warnings for bad sequence bounding index designator arguments to sequence functions. * enhancement: The sb-mpfr contrib now allows coercion from MPFR-FLOATs to CL:RATIONAL. (Thanks to Robert Smith) * bug fix: fix compilation failure related to declaiming types of constants. (lp#1977726, reported by Pierre Neidhardt) * bug fix: fix race condition in CLOS optimized constructors. (lp#1951341) * bug fix: fix too-eager elision of allocation barriers when initializing closure and structure objects. * optimization: fasl files are now usually smaller (up to 10% on default policy) and may load faster, especially on high debug. * optimization: faster string comparisons on arm64, x86-64. * optimization: faster [n]string-down/upcase on arm64, x86-64. * optimization: faster [n]reverse for 8- and 32-bit element vectors on arm64, x86-64. * optimization: faster type tests for (CONS (EQL symbol)) on x86-64.