Missing some of libsodium constants

[azjezz]

HHVM is missing some SODIUM_CRYPTO_GENERICHASH_* constants.

see : https://www.php.net/manual/en/sodium.constants.php

the missing constants :

• const int SODIUM_CRYPTO_GENERICHASH_BYTES = 32;
• const int SODIUM_CRYPTO_GENERICHASH_BYTES_MAX = 64;
• const int SODIUM_CRYPTO_GENERICHASH_BYTES_MIN = 16;

polyfill : https://github.com/nuxed/crypto/blob/master/src/Nuxed/Crypto/_Private/polyfill.hack

[fredemmott]

"Probably easy" however:

• constants must be exported from the C variables - fixed values must not be hardcoded
• older versions of libsodium might not define them - C++ code may need to use macros to conditionally set them.

[jedisct1]

These constants were added in libsodium 0.4.0 released circa 2013.

No Linux distribution is shipping a version that old.

[fredemmott]

Thanks - on the topic of sodium (but a bit off-topic for here), #8330 should probably be resurrected; previously, not merged due to reliance of reference semantics which were due to be removed, however references are now completely removed from HHVM, and the concerns have been addressed by implementation details/optimizations of inout (no copies actually made in situations when the byref approach also had a refcount of 1).