chore: mqtt impl, fix more wiznet bugs

lib/ioLibrary_Driver/MQTT/MQTTClient.h

@@ -43,6 +43,8 @@
 #define MAX_MESSAGE_HANDLERS 5 /* redefinable - how many subscriptions do you want? */
 #endif
 
+#define MAX_TOPIC_LENGTH 64
+
 enum QoS { QOS0, QOS1, QOS2 };
 
 /* all failure return codes must be negative */
@@ -97,7 +99,7 @@ typedef struct MQTTClient
 
     struct MessageHandlers
     {
-        const char* topicFilter;
+        char topicFilter[MAX_TOPIC_LENGTH];
         void (*fp) (MessageData*);
     } messageHandlers[MAX_MESSAGE_HANDLERS];      /* Message handlers are indexed by subscription topic */