`LZ4_DISTANCE_MAX` : control the maximum offset that the compressor will allow. Set to 65535 by default, which is the maximum value supported by lz4 format.
Reducing maximum distance will reduce opportunities for LZ4 to find matches,
hence will produce worse the compression ratio.

The above is true for high compression modes, i.e., levels above 3, but the opposite is true for compression levels 1 and 2.

Here is a test result using default value ( 65535 ):

<TestData> lz4-v1.9.1 -b1 enwik8 1#enwik8 : 100000000 -> 57262281 (1.746), 325.6 MB/s ,2461.0 MB/s

and result using a smaller value ( 32767 ):
<TestData> lz4-1.9.1-32 -b1 enwik8
1#enwik8 : 100000000 -> 53005796 (1.887), 239.3 MB/s ,2301.1 MB/s

Anything unusual in LZ4_compress_generic() implementation? Could anyone shed some light? Thanks in advance.