Didn't add dll folder since it wasn't copied when updating zstd to
1.3.4.
Didn't add extra files from the lib directory (Makefile, README.md, etc)
that were also left out when updating zstd to 1.3.4.
Add new zstd files to setup_zstd.py (DDict was refactored in
facebook/zstd#1388)
setup_zstd.py modified so it is just amending the Extension() kwargs,
but the Extension is initialized by the caller.
this way, amending can happend multiple times (e.g. for multiple
compression algorithms).
also:
- move include/library dirs processing for system-library case
- move system zstd prefix detection to setup_zstd module
- cosmetic: setup.py whitespace fixes
- prefer system zstd option, document zstd min. requirement
crc32_slice_by_8.c:344:3: error: ISO C90 forbids mixed declarations
and code [-Werror=declaration-after-statement]
(cherry picked from commit 23a1d62b25)
setup.py excludes all .c .h .pyx files from installation, but such
docs / license files would still be copied to the target directory
if they are inside the python "borg" package dir.
(cherry picked from commit 831a06a07d)
fixing only the (generic) slice-by-8 crc32 implementation,
it is assumed that CPUs supporting CLMUL can also efficiently
and correctly deal with unaligned accesses.
slice-by-8 is used e.g. on ARM cpus and they might not (efficiently)
support unaligned memory access, leading to bus errors or low
performance.
