A number of corrections of the aep engine implementation:

1. rnd_reference was a duplication of the work the the engine
   framework does, and wasn't ever checked.  Removed.
2. use the NO_ macros to disable appropriate algorithms.
3. Only implement the RNG stuff if AEPRAND is defined (default: not
   defined, because the AEP people plan on having boards without it.
   I'll see if I can device a more dynamic way of disabling this).
4. aep_finish() now closes all connections, and if that worked, does a
   proper finalize.
5. proper AEP types are used to conform to the AEP definitions of
   their own functions.
6. remake the use of thread locks.  The use of CRYPTO_LOCK_DYNLOCK was
   definitely inappropriate, and for random generator stuff, it's
   better to use CRYPTO_LOCK_RAND.

Also, I applied certain changes that were provided by the AEP people.
Among others, BN_CTX_new() is not used to initialise a BN context
(this was never done before, and may have made things slower or not
working at all.

crypto/engine/engine_err.c

@@ -188,12 +188,15 @@ static ERR_STRING_DATA ENGINE_str_reasons[]=
 {ENGINE_R_BN_CTX_FULL                    ,"BN_CTX full"},
 {ENGINE_R_BN_EXPAND_FAIL                 ,"bn_expand fail"},
 {ENGINE_R_CHIL_ERROR                     ,"chil error"},
+{ENGINE_R_CLOSE_HANDLES_FAILED           ,"close handles failed"},
 {ENGINE_R_CONFLICTING_ENGINE_ID          ,"conflicting engine id"},
+{ENGINE_R_CONNECTIONS_IN_USE             ,"connections in use"},
 {ENGINE_R_CTRL_COMMAND_NOT_IMPLEMENTED   ,"ctrl command not implemented"},
 {ENGINE_R_DSO_FAILURE                    ,"DSO failure"},
 {ENGINE_R_ENGINE_IS_NOT_IN_LIST          ,"engine is not in the list"},
 {ENGINE_R_FAILED_LOADING_PRIVATE_KEY     ,"failed loading private key"},
 {ENGINE_R_FAILED_LOADING_PUBLIC_KEY      ,"failed loading public key"},
+{ENGINE_R_FINALIZE_FAILED                ,"finalize failed"},
 {ENGINE_R_FINISH_FAILED                  ,"finish failed"},
 {ENGINE_R_GET_HANDLE_FAILED              ,"could not obtain hardware handle"},
 {ENGINE_R_GET_RANDOM_FAILED              ,"get random failed"},