Add some missing CHANGES items.

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

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

         +) applies to 0.9.7 only

         +) applies to 0.9.7 only

  *) Change the various "***_up()" functions, that increment reference

     counts on the various structure types, to "***_up_ref()". The naming

     is more consistent with existing code and generally a better choice.

     [Bodo Moeller]

  *) Alter all existing ENGINE implementations (except "openssl" and

     "openbsd") to dynamically instantiate their own error strings. This

     makes them more flexible to be built both as statically-linked ENGINEs

     and self-contained shared-libraries loadable via the "dynamic" ENGINE.

     Also, add stub code to each that makes building them as self-contained

     shared-libraries easier (see README.ENGINE).

     [Geoff Thorpe]

  *) Add a "dynamic" ENGINE that provides a mechanism for binding ENGINE

     implementations into applications that are completely implemented in

     self-contained shared-libraries. The "dynamic" ENGINE exposes control

     commands that can be used to configure what shared-library to load and

     to control aspects of the way it is handled. Also, made an update to

     the README.ENGINE file that brings its information up-to-date and

     provides some information and instructions on the "dynamic" ENGINE

     (ie. how to use it, how to build "dynamic"-loadable ENGINEs, etc).

     [Geoff Thorpe]

  *) BN_sqr() bug fix.

  *) BN_sqr() bug fix.

     [Ulf Möller, reported by Jim Ellis <jim.ellis@cavium.com>]

     [Ulf Möller, reported by Jim Ellis <jim.ellis@cavium.com>]