Document recent changes.

         *) applies to 0.9.6a (/0.9.6b) and 0.9.7

         +) applies to 0.9.7 only

  *) Enhance the general user interface with mechanisms for inner control

     and with pssibilities to have yes/no kind of prompts.

     [Richard Levitte]

  *) Change all calls to low level digest routines in the library and

     applications to use EVP. Add missing calls to HMAC_cleanup() and

     don't assume HMAC_CTX can be copied using memcpy().