v0.4.0

• perf: CRC-16, CRC-32 and CRC-64 checksums are computed with SIMD carry-less multiplication (PCLMULQDQ/VPCLMULQDQ on x86, PMULL on aarch64, table-based fallback elsewhere) via the crc-fast <https://crates.io/crates/crc-fast>_ crate, and CRC-8 uses slice-by-16 tables; large inputs are over 100x faster on CPUs with VPCLMULQDQ, results are unchanged.
• perf: the GIL is released while computing checksums of inputs of 16 KiB or more.
• perf: release builds use fat LTO, reducing per-call overhead for small inputs.
• perf: the functions in fastcrc.crc8/crc16/crc32/crc64 are now the extension functions themselves instead of Python wrappers around them, saving about 15 ns per call; names, positional and keyword calling and results are unchanged, type hints moved to .pyi stubs, and the note below lists what changes about the function objects.
• perf: inputs shorter than 8 bytes are computed with a lookup table, avoiding the SIMD setup cost.
• feat: every function accepts any bytes-like object (bytearray, memoryview, array, mmap, NumPy arrays, ...) through the buffer protocol, treated as raw bytes like zlib.crc32 does; bytes keeps its zero-copy fast path, and as with hashlib a mutable buffer must not be modified by another thread while its checksum is computed. Unsupported objects raise the standard a bytes-like object is required TypeError and non-contiguous buffers raise BufferError.
• chore: the crc crate is no longer a dependency; building from source requires Rust 1.89 or newer.
• note: the public functions are now built-in functions rather than Python functions: inspect.isfunction is false, they have no __annotations__, __code__ or __dict__ (attributes cannot be set on them), they do not bind as methods when stored on a class, and they do not appear as frames in tracebacks or sys.settrace; the private, undocumented fastcrc.fastcrc.crc_32_iscsi-style names and fastcrc.crc32._crc_32_iscsi-style aliases no longer exist.
• deprecation: this is the last release series to support Python 3.7; fastcrc 0.5.0 will drop it.