[gnome-music] libgd: update to latest version

[Felipe Borges <felipeborges src gnome org>]

commit a173f2ddfa4bdd9b5c1c1b66be9a6ff14d2e8ccd
Author: Felipe Borges <felipeborges gnome org>
Date:   Tue Mar 15 13:07:46 2016 +0100

    libgd: update to latest version
    
    Fixed gtk+ warnings

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 7e0dd4b..56a19ad 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 7e0dd4b15ea80673f62249ac092763b10fc226ad
+Subproject commit 56a19ad9b056332ef07e508f1bdb6f03c6cb2590