Use export declaration for the thread-related functions otherwise test2 fail to…

Use export declaration for the thread-related functions otherwise test2 fail to link with project libraries
Signed-off-by: Otavio Rodolfo Piske <opiske@redhat.com>

src/Thread.h

@@ -15,6 +15,7 @@
  *    Ian Craggs, Allan Stockdill-Mander - async client updates
  *    Ian Craggs - fix for bug #420851
  *******************************************************************************/
+#include "MQTTClient.h"
 
 #if !defined(THREAD_H)
 #define THREAD_H
@@ -46,14 +47,14 @@
 	int Thread_destroy_cond(cond_type);
 #endif
 
-thread_type Thread_start(thread_fn, void*);
+DLLExport thread_type Thread_start(thread_fn, void*);
 
-mutex_type Thread_create_mutex();
-int Thread_lock_mutex(mutex_type);
-int Thread_unlock_mutex(mutex_type);
+DLLExport mutex_type Thread_create_mutex();
+DLLExport int Thread_lock_mutex(mutex_type);
+DLLExport int Thread_unlock_mutex(mutex_type);
 void Thread_destroy_mutex(mutex_type);
 
-thread_id_type Thread_getid();
+DLLExport thread_id_type Thread_getid();
 
 sem_type Thread_create_sem();
 int Thread_wait_sem(sem_type sem, int timeout);