libsodium >= 0.6.0 is required
Merge branch 'master' of https://github.com/jedisct1/libsodium-php

* 'master' of https://github.com/jedisct1/libsodium-php:
  check for crypto_pwhash_scryptsalsa208sha256 instead of sodium init
  honour --with-libdir option (can be "lib64")