Support for non-legacy lz4 stream format

[mpartio]

Hi,

boost_lz4_filter does not support non-legacy lz4 stream format:

$ echo "This is a test file" > out.txt
$ lz4 out.txt out.txt.lz4
Compressed 20 bytes into 39 bytes ==> 195.00%                                  
$ ./lz4fcli -d < out.txt.lz4 > out
$ file out
out: empty

With legacy mode:

$ lz4 -l out.txt out.txt.lz4
Warning : out.txt.lz4 already exists
Overwrite ? (Y/N) : y
Compressed 20 bytes into 30 bytes ==> 150.00%                                  
$ ./lz4fcli -d < out.txt.lz4 > out
$ file out
out: ASCII text
$ cat out
This is a test file

$ lz4 -V
*** LZ4 Compression CLI 64-bits r124, by Yann Collet (Dec  6 2014) ***

According to the author of lz4, the legacy stream is deprecated and using it is not adviced. Any plans for adding support for this newer stream format?

Thanks,

Mikko