fixing off-by-one error in lz4.c

[Blake Childress]

LZ4 is subject to a heap-based overflow in some use cases. More details found here: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2019-17543

Fix can be made by adding one symbol in lz4.c, found here: https://github.com/lz4/lz4/commit/d7cad81093cd805110291f84d64d385557d0ffba

Since pull requests are not enabled, hopefully this issue finds you well :D

[Andrey Ugolnik]

Thanks, I have updated the LZ4 module to v1.9.3.