Blosc

Fixed a buffer overrun that happens when compressing small buffers and
`len(destination_buffer) < len(source_buffer) + BLOSC_MAX_OVERHEAD'.
Thanks to Ivan Smirnov for reporting this.

Tests should work now when external compressors are located in non-system locations. Fixes 210. Thanks to Leif Walsh.

- C-Blosc can be compiled on CentOS 6 now.

- LZ4 internal codec upgraded to 1.8.1.

For more info, please see the release notes in:

https://github.com/Blosc/c-blosc/blob/master/RELEASE_NOTES.rst

Fixed a bug uncovered by the python-blosc test suite: when a buffer is
to be copied, then we should reserve space for the header, not block
pointers.

For more info, please see the release notes in:

https://github.com/Blosc/c-blosc/blob/master/RELEASE_NOTES.rst

A serious optimization of memory copy functions (see `blosc/fastcopy.c`) .
This benefits the speed of all the codecs, but specially the BloscLZ one.
As a result of the above, the BloscLZ codec received a new adjustment of
knobs so that you should expect better compression ratios with BloscLZ too.

Also, the LZ4 codec internal sources have been updated to 1.8.0. And internal
Zstd sources have been updated to 1.3.3 too.

Backported BloscLZ parameters that were fine-tuned for C-Blosc2.
You should expect better compression ratios and faster operation,
specially on modern CPUs. See:
http://blosc.org/posts/blosclz-tuning/