libsodium: create recipe

zeromq 4.1.3 requires libsodium

Sodium is a new, easy-to-use software library for encryption, decryption,
signatures, password hashing and more. It is a portable, cross-compilable,
installable, packageable fork of NaCl, with a compatible API, and an extended
API to improve usability even further. Its goal is to provide all of the core
operations needed to build higher-level cryptographic tools. The design
choices emphasize security, and "magic constants" have clear rationales.

The same cannot be said of NIST curves, where the specific origins of certain
constants are not described by the standards. And despite the emphasis on
higher security, primitives are faster across-the-board than most
implementations of the NIST standards.

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>