[gnome-music/gnome-3-18] Update libgd

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit 98ee58a3a3a9a36f74c1283470e621b8c6e464cd
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Thu Sep 24 15:51:29 2015 -0700

    Update libgd
    
    https://bugzilla.gnome.org/show_bug.cgi?id=755601

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 7e0dd4b..ed6c8f3 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 7e0dd4b15ea80673f62249ac092763b10fc226ad
+Subproject commit ed6c8f3667b67ac284933a3d03faa34b5948bf52