[gtk+] Only include vulkan.h if we have it

[Matthias Clasen <matthiasc src gnome org>]

commit 5b6a837b1731b61ee841e9c58e8b5171bb817a7a
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 9 14:05:26 2016 -0500

    Only include vulkan.h if we have it

 gdk/gdkvulkancontext.c        |    4 +++-
 gdk/gdkvulkancontextprivate.h |    2 ++
 2 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkvulkancontext.c b/gdk/gdkvulkancontext.c
index 399cd98..c5763c4 100644
--- a/gdk/gdkvulkancontext.c
+++ b/gdk/gdkvulkancontext.c
@@ -1,6 +1,6 @@
 /* GDK - The GIMP Drawing Kit
  *
- * gdkvulkancontext-x11.c: X11 specific Vulkan wrappers
+ * gdkvulkancontext.c: Vulkan wrappers
  *
  * Copyright © 2016  Benjamin Otte
  *
@@ -22,7 +22,9 @@
 
 #include "gdkvulkancontextprivate.h"
 
+#ifdef GDK_WINDOWING_VULKAN
 #include <vulkan/vulkan.h>
+#endif
 
 #include "gdkdisplayprivate.h"
 #include "gdkinternals.h"
diff --git a/gdk/gdkvulkancontextprivate.h b/gdk/gdkvulkancontextprivate.h
index 1d56de8..42fdbac 100644
--- a/gdk/gdkvulkancontextprivate.h
+++ b/gdk/gdkvulkancontextprivate.h
@@ -26,7 +26,9 @@
 #include "gdkdrawcontextprivate.h"
 #include "gdkinternals.h"
 
+#ifdef GDK_WINDOWING_VULKAN
 #include <vulkan/vulkan.h>
+#endif
 
 G_BEGIN_DECLS