[gtk/remove-deprecations] Add a missing include

[Matthias Clasen <matthiasc src gnome org>]

commit 1ea1decfd69cd119b95f4061e37d0204ad31e5d6
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Mar 29 11:55:42 2019 -0400

    Add a missing include

 gdk/gdkseatdefault.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gdk/gdkseatdefault.c b/gdk/gdkseatdefault.c
index 14dbb75f97..22b4b64e9b 100644
--- a/gdk/gdkseatdefault.c
+++ b/gdk/gdkseatdefault.c
@@ -19,6 +19,7 @@
 
 #include "gdkseatdefaultprivate.h"
 #include "gdkdevicetoolprivate.h"
+#include "gdkinternals.h"
 
 typedef struct _GdkSeatDefaultPrivate GdkSeatDefaultPrivate;