Missing docs for crypto:md4, new crypto:des_ecb_encrypt and crypto:des_ecb_decrypt funs.

[Alexander Uvarov]

Hi, team.

* Added missing docs for md4 and friends. Let people know about it.
* 2 new useful functions des_ecb_encrypt and des_ecb_decrypt. Tests and docs are included.

Quote from "man des": DES_ecb_encrypt() is the basic DES encryption routine that encrypts or decrypts a single 8-byte DES_cblock in electronic code book (ECB) mode.


git fetch git://github.com/wildchild/otp.git crypto
View online: http://github.com/wildchild/otp/commits/crypto

Crypto test suite with these changes passes on OSX 10.6.