[gnome-font-viewer] Add missing include

[Cosimo Cecchi <cosimoc src gnome org>]

commit c74a6a0e6511bba70c24bc60d511a615e150d2ac
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Sat Nov 21 13:29:05 2015 -0800

    Add missing include

 src/sushi-font-widget.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/sushi-font-widget.c b/src/sushi-font-widget.c
index 4bf75b7..1b7febd 100644
--- a/src/sushi-font-widget.c
+++ b/src/sushi-font-widget.c
@@ -27,6 +27,7 @@
 #include "sushi-font-widget.h"
 #include "sushi-font-loader.h"
 
+#include <hb-glib.h>
 #include <math.h>
 
 enum {