ENGINE module additions.

Add "init" command to control ENGINE
initialization.

Call ENGINE_finish on initialized ENGINEs on exit.

Reorder shutdown in apps.c: modules should be shut
down first.

Add test private key loader to openssl ENGINE: this
just loads a private key in PEM format.

Fix print format for dh length parameter.

crypto/engine/engine.h

@@ -707,6 +707,7 @@ void ERR_load_ENGINE_strings(void);
 #define ENGINE_R_INVALID_ARGUMENT			 143
 #define ENGINE_R_INVALID_CMD_NAME			 137
 #define ENGINE_R_INVALID_CMD_NUMBER			 138
+#define ENGINE_R_INVALID_INIT_VALUE			 151
 #define ENGINE_R_INVALID_STRING				 150
 #define ENGINE_R_NOT_INITIALISED			 117
 #define ENGINE_R_NOT_LOADED				 112