Add CHANGES entry for X25519

 Changes between 1.0.2f and 1.1.0  [xx XXX xxxx]

  *) Add X25519 support.

     Integrate support for X25519 into EC library. This includes support

     for public and private key encoding using the format documented in

     draft-josefsson-pkix-newcurves-01: specifically X25519 uses the

     OID from that draft, encodes public keys using little endian

     format in the ECPoint structure and private keys using

     little endian form in the privateKey field of the ECPrivateKey

     structure. TLS support complies with draft-ietf-tls-rfc4492bis-06

     and uses X25519(29).

     Note: the current version supports key generation, public and

     private key encoding and ECDH key agreement using the EC API.

     Low level point operations such as EC_POINT_add(), EC_POINT_mul()

     are NOT supported.

     [Steve Henson]

  *) Deprecate SRP_VBASE_get_by_user.

     SRP_VBASE_get_by_user had inconsistent memory management behaviour.

     In order to fix an unavoidable memory leak (CVE-2016-0798),