rtos :introduce possible overload by rtos of gdb_thread_packet

Change-Id: I17381b581556fa75098a84699dbbf69423fe20eb
Signed-off-by: Michel JAOUEN <michel.jaouen@stericsson.com>
Reviewed-on: http://openocd.zylin.com/342
Tested-by: jenkins
Reviewed-by: Evan Hunter <evan@ozhiker.com>
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>

src/rtos/rtos.h

@@ -61,9 +61,10 @@ struct rtos
 	threadid_t current_thread;
 	struct thread_detail* thread_details;
 	int thread_count;
-
+	int (*gdb_thread_packet)(struct connection *connection, char *packet, int packet_size);
 	void * rtos_specific_params;
 
+
 };