[clutter-gtkmm] Avoid attribute warn_unused_result compiler warning.

[Murray Cumming <murrayc src gnome org>]

commit da62b18e98d6ec1c7a00f5be92e21315014516f8
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Feb 24 20:44:11 2016 +0100

    Avoid attribute warn_unused_result compiler warning.

 .../extradefs/generate_extra_defs_clutter_gtk.cc   |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/codegen/extradefs/generate_extra_defs_clutter_gtk.cc 
b/codegen/extradefs/generate_extra_defs_clutter_gtk.cc
index 4be1f95..4e7c4ec 100644
--- a/codegen/extradefs/generate_extra_defs_clutter_gtk.cc
+++ b/codegen/extradefs/generate_extra_defs_clutter_gtk.cc
@@ -19,15 +19,19 @@
 #include <clutter/clutter.h>
 #include <clutter-gtk/clutter-gtk.h>
 #include <iostream>
+#include <cstdlib>
 
 int main(int argc, char** argv)
 {
-  clutter_init(&argc, &argv);
+  if(clutter_init(&argc, &argv) != CLUTTER_INIT_SUCCESS)
+  {
+    return EXIT_FAILURE;
+  }
 
   std::cout
     << get_defs(GTK_CLUTTER_TYPE_ACTOR)
     << get_defs(GTK_CLUTTER_TYPE_EMBED)
     << get_defs(GTK_CLUTTER_TYPE_WINDOW);
 
-  return 0;
+  return EXIT_SUCCESS;
 }