Changes
   * Add the command line parameter key_pwd to the ssl_client2 and ssl_server2
     example applications which allows to provide a password for the key file
     specified through the existing key_file argument. This allows the use of
     these applications with password-protected key files. Analogously but for
     ssl_server2 only, add the command line parameter key_pwd2 which allows to
     set a password for the key file provided through the existing key_file2
     argument.