Fix a bunch of warnings.

examples/nfc-emulate-tag.c

@@ -63,6 +63,7 @@ static bool init_mfc_auth = false;
 static void
 intr_hdlr (int sig)
 {
+  (void) sig;
   printf ("\nQuitting...\n");
   if (pnd != NULL) {
     nfc_close(pnd);    

examples/nfc-emulate-uid.c

@@ -68,6 +68,7 @@ uint8_t  abtSak[9] = { 0x08, 0xb6, 0xdd };
 static void
 intr_hdlr (int sig)
 {
+  (void) sig;
   if (pnd != NULL) {
     printf ("\nAborting current command...\n");
     nfc_abort_command (pnd);

examples/nfc-relay.c

@@ -63,6 +63,7 @@ static bool quitting = false;
 static void
 intr_hdlr (int sig)
 {
+  (void) sig;
   printf ("\nQuitting...\n");
   quitting = true;
   return;