the tracee (lte-softmodem) now sends the content of T_messages.txt

as special events.

If we store all received events to a file, this dump is now
self-contained. Helps to analyze traces.

Some functions have also been factorized in the process, too much
duplication.

(Also tracer/Makefile was forgotten in previous commit, included
in this one...)

common/utils/T/tracer/utils.h

@@ -21,6 +21,8 @@ list *list_append(list *l, void *data);
 /****************************************************************************/
 
 void socket_send(int socket, void *buffer, int size);
+int get_connection(char *addr, int port);
+int fullread(int fd, void *_buf, int count);
 
 /****************************************************************************/
 /* buffer                                                                   */