Blosc2

* Updated to latest C-Blosc2 2.13.1.

* Fixed bug in `b2nd.h`.

* Updated to latest C-Blosc2 2.13.0.

* Added the filter `INT_TRUNC` for integer truncation.

* Added some optimizations for zstd.

* Now the grok library is initialized when loading the
plugin from C-Blosc2.

* Improved doc.

* Support for slices in ``blosc2.get_slice_nchunks()`` when using SChunk
objects.

===========================

* Disable automatic split of blocks when not using shuffle. Experiments are showing that cratio is suffering too much, specially when using BloscLZ.

* Changed xxhash.h and xxhash.c to the newest version. Thanks to Dimitri Papadopoulos.

===========================

* Fixed BLOSC1_COMPAT mode. If the symbol `BLOSC1_COMPAT` is defined, one should actually get a correct map for the BLOSC1 API now. Thanks to MehdiChinoune for pointing this out.

* Optimizations for `blosc2_schunk_get_slice_buffer()`. Now more caution has been put in avoiding memcpy's as much as possible.

* Now `blosc2_set_nthreads()` also modifies the schunk compression and decompression defaults.

* Several other fixes, specially when converting schunks to cframe format.

===========================

* New `blosc2_schunk_avoid_cframe_free()` for avoiding the free of a cframe when destroying a super-chunk. Mainly useful for situations where you build a super-chunk out of an existing cframe, so you don't want it to be freed automatically.

* Updated to latest C-Blosc2 2.12.0.

* Added `blosc2.get_slice_nchunks()` to get array of chunk
indexes needed to get a slice of a Blosc2 container.

* Added grok codec plugin.

* Added imported target with pkg-config to support windows.