Add changes entry for opaquifying of libssl structures

Reviewed-by: NRichard Levitte <levitte@openssl.org>

CHANGES

@@ -3,6 +3,11 @@
  _______________
 
  Changes between 1.0.2 and 1.1.0  [xx XXX xxxx]
+  *) All libssl internal structures have been removed from the public header
+     files, and the OPENSSL_NO_SSL_INTERN option has been removed (since it is
+     now redundant). Users should not attempt to access internal structures
+     directly. Instead they should use the provided API functions.
+     [Matt Caswell]
 
   *) config has been changed so that by default OPENSSL_NO_DEPRECATED is used.
      Access to deprecated functions can be re-enabled by running config with