[gnome-desktop] gnome-languages: Add missing glib include

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 555b6275e9f6f87886fd7a6c69fd1984b53adef4
Author: Robert Ancell <robert ancell canonical com>
Date:   Mon Aug 13 12:01:21 2018 +1200

    gnome-languages: Add missing glib include
    
    Include glib.h at the start of the language header, otherwise a program using
    this header will get errors if it hasn't already included it.

 libgnome-desktop/gnome-languages.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/libgnome-desktop/gnome-languages.h b/libgnome-desktop/gnome-languages.h
index 3d7525d9..407a8c3b 100644
--- a/libgnome-desktop/gnome-languages.h
+++ b/libgnome-desktop/gnome-languages.h
@@ -27,6 +27,8 @@
 #error    This is unstable API. You must define GNOME_DESKTOP_USE_UNSTABLE_API before including 
gnome-languages.h
 #endif
 
+#include <glib.h>
+
 G_BEGIN_DECLS
 
 char *        gnome_get_language_from_locale    (const char *locale,