use packCStringLen to avoid truncating the raw hash on the first NULL
use packCStringLen to avoid truncating the raw hash on the first NULL

Fixes https://github.com/ocharles/argon2/issues/3

hashEncoded' still uses packCString, because there the encoded string does
in fact end at NULL.

ocharles/argon2,ocharles/argon2,ocharles/argon2