[gnome-music/gnome-3-16] Update libgd

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit d76d2e5d07a7c9b17054755e9fa8330c4c02d155
Author: Vadim Rutkovsky <vrutkovs redhat com>
Date:   Tue Aug 11 11:09:00 2015 +0200

    Update libgd

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 643ad53..8af0b5d 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 643ad53887f6507a775c1f6e1cfbbbe4e939b043
+Subproject commit 8af0b5d665b309c455b7d337f36e258f253bd599