Merge pull request DataDog#73 from dbenamydd/1.x

Update zstd to version 1.4.4

Merge pull request DataDog#64 from bai/zstd-1.4.1

Update zstd to version 1.4.1

Merge pull request DataDog#58 from bai/zstd-1.4.0

Update vendored zstd to 1.4.0

Merge pull request DataDog#56 from DataDog/viq111/keepalive

[zstd] Properly keep alive src

Merge pull request DataDog#45 from DataDog/viq111/arch32

Fix tests for 32 bits systems and provide an env to test it

Merge pull request DataDog#31 from valyala/remove-mallocs-from-compre…

…ss-decompress

Remove mallocs from Compress/Decompress

Merge pull request DataDog#18 from DataDog/elijah/1.3.0

Update zstd to 1.3.0

Merge pull request DataDog#2 from DataDog/jason/zlib-conformity

match zlib library interface and documentation where appliccable