Remove MBEDTLS_SSL_AEAD_RANDOM_IV feature

In a USENIX WOOT '16 paper the authors warn about a security risk
of random Initialisation Vectors (IV) repeating values.

The MBEDTLS_SSL_AEAD_RANDOM_IV feature is affected by this risk and
it isn't compliant with RFC5116. Furthermore, strictly speaking it
is a different cipher suite from the TLS (RFC5246) point of view.

Removing the MBEDTLS_SSL_AEAD_RANDOM_IV feature to resolve the above
problems.

Hanno Böck, Aaron Zauner, Sean Devlin, Juraj Somorovsky and Philipp
Jovanovic, "Nonce-Disrespecting Adversaries: Practical Forgery Attacks
on GCM in TLS", USENIX WOOT '16
diff --git a/ChangeLog b/ChangeLog
index 6813b34..e85af2e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,10 @@
 = mbed TLS 2.1.x branch released 2016-xx-xx
 
 Security
+   * Remove MBEDTLS_SSL_AEAD_RANDOM_IV option, because it was not compliant
+     with RFC5116 and could lead to session key recovery in very long TLS
+     sessions. (H. Bock, A. Zauner, S. Devlin, J. Somorovsky, P. Jovanovic -
+     "Nonce-Disrespecting Adversaries Practical Forgery Attacks on GCM in TLS")
    * Fix potential stack corruption in mbedtls_x509write_crt_der() and
      mbedtls_x509write_csr_der() when the signature is copied to the buffer
      without checking whether there is enough space in the destination. The