[gnome-system-log] Update to latest libgd

[Cosimo Cecchi <cosimoc src gnome org>]

commit ed87f3ca30f6c08f5b9c38b88a749a76c6912922
Author: Carl-Anton Ingmarsson <ca ingmarsson gmail com>
Date:   Sat Feb 9 18:14:39 2013 +0100

    Update to latest libgd
    
    https://bugzilla.gnome.org/show_bug.cgi?id=693485

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 3b110dd..4cd7128 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 3b110dd27b65e5dc6591bfcbbf1799f549ce0d34
+Subproject commit 4cd7128e3b6c3dbafc4b1839585e69885b9f4741