[libdazzle] multi-paned: use IS_HORIZONTAL() macro

[Christian Hergert <chergert src gnome org>]

commit 97840f61a3f053cdaa738f7113e5f3d7833c710a
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jun 21 16:42:39 2017 -0700

    multi-paned: use IS_HORIZONTAL() macro
    
    This should stay consistent with other code in the module.

 src/widgets/dzl-multi-paned.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/widgets/dzl-multi-paned.c b/src/widgets/dzl-multi-paned.c
index e167021..ee29ee7 100644
--- a/src/widgets/dzl-multi-paned.c
+++ b/src/widgets/dzl-multi-paned.c
@@ -1332,7 +1332,7 @@ allocation_stage_allocate (DzlMultiPaned   *self,
         {
           if (state->n_children != (i + 1))
             {
-              if (state->orientation == GTK_ORIENTATION_HORIZONTAL)
+              if (IS_HORIZONTAL (state->orientation))
                 {
                   gdk_window_move_resize (child->handle,
                                           child->alloc.x + child->alloc.width - (HANDLE_WIDTH / 2),