Enhancement request: expose chunk_cut_fingerprint in JS out stream object

[green-coder]

chunk_cut_fingerprint is not only useful inside the low level splitting algorithm. It can also be used by the JS program to group the sha256 hashes by using the upper bits (above the 14th bit) as delimiters. The idea is to have a merkel tree with a depth higher than 2, this is very needed for handling large files (1~2 GB).

I would be happy to implement the change myself, but I do not master the build process for C bind yet.