Problem: classification ZMQ_HANDSHAKE_FAILED_* events is coarse-grained and partially misleading

Solution: redesign ZMQ_HANDSHAKE_FAILED_* events, introduce new class of ZMQ_HANDSHAKE_FAILED_AUTH events

src/mechanism.hpp

@@ -53,14 +53,6 @@ namespace zmq
             error
         };
 
-        //  Provides more details when in status_t::error
-        enum error_detail_t {
-            no_detail,
-            zmtp,
-            zap,
-            encryption
-        };
-
         mechanism_t (const options_t &options_);
 
         virtual ~mechanism_t ();
@@ -81,10 +73,6 @@ namespace zmq
         //  Returns the status of this mechanism.
         virtual status_t status () const = 0;
 
-        //  Returns details about of the current error of the mechanism.
-        //  Returned value does not makes sense if the current status is not error.
-        virtual error_detail_t error_detail () const { return no_detail; }
-
         void set_peer_identity (const void *id_ptr, size_t id_size);
 
         void peer_identity (msg_t *msg_);