Putting back SIGINT detection for lte-softmodem and initial skeleton to retrieve runtime stats from eNB/gNB

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

targets/RT/USER/lte-softmodem.c

@@ -556,6 +556,8 @@ int main ( int argc, char **argv )
 
   MSC_INIT(MSC_E_UTRAN, THREAD_MAX+TASK_MAX);
   init_opt();
+  // to make a graceful exit when ctrl-c is pressed
+  set_softmodem_sighandler();
   check_clock();
 #ifndef PACKAGE_VERSION
 #  define PACKAGE_VERSION "UNKNOWN-EXPERIMENTAL"