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/event.h

@@ -37,6 +37,8 @@ typedef struct {
   int ecount;
 } event;
 
+event get_event(int s, char *v, void *d);
+
 #ifdef T_SEND_TIME
 event new_event(struct timespec sending_time, int type,
     int length, char *buffer, void *database);