Add pmemkv_put_emplace function

[igchor]

We should add pmemkv_put_emplace(pmemkv_db *db, callback, size) function which would allow to insert data without any copy. Morever, user would not have to prepare any buffer, he can just put data straight to the pmem.

[JerryYangSH]

It looks I have no permission to access the repo. Could you grant me?

jerry@u19:~/opensources/pmemkv$ git push --set-upstream origin pmemkv-stree-get-above Username for 'https://github.com': JerryYangSH Password for 'https://[email protected]': remote: Permission to pmem/pmemkv.git denied to JerryYangSH. fatal: unable to access 'https://github.com/pmem/pmemkv.git/': The requested URL returned error: 403