support lz4 compress&uncompress

[t00350320]

please help to review my pr. as discussed in https://github.com/google/leveldb/issues/721 , lz4 compress show a good performance on compress&uncompress . I have tested in leveldb_bench :

root@xx:/opt/opensource/level-lz4/leveldb/build# ./db_bench 
LevelDB:    version 1.23
Date:       Wed Jan 12 20:04:52 2022
CPU:        4 * Intel(R) Xeon(R) Gold 6150 CPU @ 2.70GHz
CPUCache:   25344 KB
Keys:       16 bytes each
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)

fillseq      :       2.441 micros/op;   45.3 MB/s     
fillsync     :    2612.438 micros/op;    0.0 MB/s (1000 ops)
fillrandom   :       5.780 micros/op;   19.1 MB/s     
overwrite    :      10.133 micros/op;   10.9 MB/s     
readrandom   :      12.942 micros/op; (864322 of 1000000 found)
readrandom   :      11.557 micros/op; (864083 of 1000000 found)
readseq      :       0.348 micros/op;  317.5 MB/s    
readreverse  :       0.439 micros/op;  251.8 MB/s    
compact      : 2026325.000 micros/op;
readrandom   :       9.479 micros/op; (864105 of 1000000 found)
readseq      :       0.377 micros/op;  293.8 MB/s    
readreverse  :       0.422 micros/op;  262.4 MB/s    
fill100K     :    2655.037 micros/op;   35.9 MB/s (1000 ops)
crc32c       :       1.346 micros/op; 2901.7 MB/s (4K per op)
snappycomp   :      40.606 micros/op;   96.2 MB/s (output: 55.1%)
snappyuncomp :       2.695 micros/op; 1449.3 MB/s    
lz4comp      :       4.279 micros/op;  912.9 MB/s (output: 55.2)
lz4uncomp    :       0.494 micros/op; 7905.0 MB/s