md5 - md5 hashing

`local md5 = require'md5'`

A ffi binding of the popular MD5 implementation by Alexander Peslyak.

`md5.sum(s[, size]) -> s` `md5.sum(cdata, size) -> s`	Compute the MD5 sum of a string or a cdata buffer. Returns the binary representation of the hash. To get the hex representation, use glue.tohex.
`md5.digest() -> digest` `digest(s[, size])` `digest(cdata, size)` `digest() -> s`	Get a MD5 digest function that can consume multiple data chunks until called with no arguments when it returns the final binary MD5 hash.