Decompress sometime lead to additional garbage data

[sidd1809]

Issue starting in version: v4.1.1 onwards
Last working Version: v4.1.0

We recently upgraded our lz4 library from v2.6.1+incompatible to v4.1.22 and started noticing data mismatch on decompression. Identified a missed edge-case handling where Decompress/Read patterns could return 0 data length, which currently ends up leaking a previously decompressed data frame buffer.

Fix: Trim data frame buffer when it is by-passed for received buffer in a Read(recvBuf []byte) call.

Testing:

• Ran all existing unit tests
• Similar benchmark number.
• Have added a unit test that consistently reproduced the data mismatch error on data size in multiple of 20MB.

[sidd1809]

@pierrec have posted a Repro test and a fix in #231