Update libsrtp to version 2.0

srtp/doc/crypto_kernel.txt

-/**
-
-@defgroup CryptoKernel Cryptographic Kernel
-
-All of the cryptographic functions are contained in a kernel.
-
-*/
-
-/**
-
-@defgroup CipherImplementations Ciphers
-@ingroup  CryptoKernel
-
-@brief A generic cipher type enables cipher agility, that is, the
-ability to write code that runs with multiple cipher types.
-Ciphers can be used through the crypto kernel, or can be accessed
-directly, if need be.
-
-@{
-
-*/
-
-/**
- * @brief Allocates a cipher of a particular type.
- * @warning May be implemented as a macro.
- */
-err_status_t
-cipher_type_alloc(cipher_type_t *ctype, cipher_t **cipher, 
-                        unsigned key_len);
-
-/**
- * @brief Initialized a cipher to use a particular key.  May
- *       be invoked more than once on the same cipher.
- * @warning May be implemented as a macro.
- */
-
-err_status_t
-cipher_init(cipher_t *cipher, const uint8_t *key);
-
-/**
- * @brief Sets the initialization vector of a given cipher.
- * @warning May be implemented as a macro.
- */
-
-err_status_t
-cipher_set_iv(cipher_t *cipher, void *iv);
-
-/**
- * @brief Encrypts a buffer with a given cipher.
- * @warning May be implemented as a macro.
- */                           
-
-err_status_t
-cipher_encrypt(cipher_t *cipher, void *buf, unsigned int *len);
-
-/**
- * @brief Sets a buffer to the keystream generated by the cipher.
- * @warning May be implemented as a macro.
- */
-err_status_t 
-cipher_output(cipher_t *c, uint8_t *buffer, int num_octets_to_output);
-
-/**
- * @brief Deallocates a cipher.
- * @warning May be implemented as a macro.
- */
-err_status_t
-cipher_dealloc(cipher_t *cipher);
-
-
-
-/**
- * @} 
- */
-
- */