Use standard C initializer list syntax

Fix clang warning

  warning: use of GNU old-style field designator extension [-Wgnu-designator]

common/utils/T/tracer/hacks/dump_nack_signal.c

@@ -85,7 +85,7 @@ int main(int n, char **v) {
       socket_send(socket, is_on, number_of_events * sizeof(int)) == -1)
     abort();
 
-  OBUF ebuf = { osize: 0, omaxsize: 0, obuf: NULL };
+  OBUF ebuf = {.osize = 0, .omaxsize = 0, .obuf = NULL};
   char dump[10][T_BUFFER_MAX];
   event dump_ev[10];
   FILE *z = fopen("/tmp/dd", "w");

common/utils/T/tracer/hacks/multi-rru-clean.c

@@ -145,7 +145,7 @@ int main(int n, char **v)
 
   clear_cache(number_of_tags, cache);
 
-  OBUF ebuf = { osize: 0, omaxsize: 0, obuf: NULL };
+  OBUF ebuf = {.osize = 0, .omaxsize = 0, .obuf = NULL};
 
   while (1) {
     int type;

common/utils/T/tracer/hacks/time_meas.c

@@ -86,7 +86,7 @@ int main(int n, char **v)
       socket_send(socket, is_on, number_of_events * sizeof(int)) == -1)
     abort();
 
-  OBUF ebuf = { osize: 0, omaxsize: 0, obuf: NULL };
+  OBUF ebuf = {.osize = 0, .omaxsize = 0, .obuf = NULL};
 
   while (1) {
     event e;