Add an exit code to make-dissectors.

Explicitly return 0 from make-dissectors on success. Hopefully this will
fix some Windows builder failures.

Change-Id: I0c172597584c52ced2380719135e8559ef83392a
Reviewed-on: https://code.wireshark.org/review/25150
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>

epan/dissectors/make-dissectors.c

@@ -196,6 +196,8 @@ int main(int argc, char **argv)
 
     printf("Found %u registrations and %u handoffs.\n",
                 count_protos, count_handoffs);
+
+    return 0;
 }
 
 /*