[gnome-documents] build: Update to latest libgd

[Debarshi Ray <debarshir src gnome org>]

commit d0e655c91015524c814ac271ef4a65e1f478cdad
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri May 12 18:11:42 2017 +0200

    build: Update to latest libgd
    
    Adds a new test case for GdTaggedEntry to mimic the widget hierarchy
    used in gnome-documents and gnome-photos. It will be useful to debug
    theming problems.

 libgd |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgd b/libgd
index 3afb334..234f224 160000
--- a/libgd
+++ b/libgd
@@ -1 +1 @@
-Subproject commit 3afb334ed1d87580df0adf34c8ed6c31e5d3d667
+Subproject commit 234f224d8cef69a1fc6dc37059cbb31fc835c4c1