Changes from 1.21.6 to 1.21.7

• Internal LZ4 codec updated to 1.10.0. Thanks to Dimitri Papadopoulos.

• Security and buffer-validation hardening:

  • Fix out-of-bounds write in blosc_getitem for negative nitems (#406).
  • Reject split blocks not covering blocksize in blosc_d (#407).
  • Reject destsize too small for block pointers in blosc_compress_context (#408).
    Thanks to Suraiya Sulthana.

• Clamp destsize to avoid int32 overflow and move getenv("BLOSC_WARN")
  out of the multi-threaded decompression path (#387, #390). Thanks to @nhz2.

• Validate that typesize is greater than zero (#395). Thanks to Barak Ugav.

• Fix compilation with GCC 15 (C23) in internal Zlib (#392). Thanks to Georg Semmler.

• Add generic RISC-V build support (#403, thanks to @carlosqwqqwq) and enable
  -std=gnu99 for GCC across all architectures (#399, thanks to Levi Zim).

• Update minimum CMake version to 3.10 for compatibility with CMake 4.x (#404).
  Thanks to @mosfet80.

• Various compiler warning fixes and documentation improvements (#380, #381, #382).
  Thanks to @nhz2, Dimitri Papadopoulos, and Richard Barnes.