[cogl] egl: forward declare wl_resource for compatibility

[Robert Bragg <rbragg src gnome org>]

commit 9bd1ee544667cfe7ecae479ec7f778446dd8f326
Author: Robert Bragg <robert linux intel com>
Date:   Mon Oct 28 14:32:20 2013 +0000

    egl: forward declare wl_resource for compatibility
    
    Depending on what version of Mesa you have then eglQueryWaylandBuffer
    may take a wl_buffer or wl_resource argument and the EGL header will
    only forward declare the corresponding type.
    
    The use of wl_buffer has been deprecated and so internally we assume
    that eglQueryWaylandBuffer takes a wl_resource but for compatibility we
    forward declare wl_resource in case we are building with EGL headers
    that still use wl_buffer.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=710926
    
    Reviewed-by: Neil Roberts <neil linux intel com>

 cogl/winsys/cogl-winsys-egl-private.h |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)
---
diff --git a/cogl/winsys/cogl-winsys-egl-private.h b/cogl/winsys/cogl-winsys-egl-private.h
index 8f33191..a1dbf26 100644
--- a/cogl/winsys/cogl-winsys-egl-private.h
+++ b/cogl/winsys/cogl-winsys-egl-private.h
@@ -30,6 +30,27 @@
 #include "cogl-context-private.h"
 #include "cogl-framebuffer-private.h"
 
+/* XXX: depending on what version of Mesa you have then
+ * eglQueryWaylandBuffer may take a wl_buffer or wl_resource argument
+ * and the EGL header will only forward declare the corresponding
+ * type.
+ *
+ * The use of wl_buffer has been deprecated and so internally we
+ * assume that eglQueryWaylandBuffer takes a wl_resource but for
+ * compatibility we forward declare wl_resource in case we are
+ * building with EGL headers that still use wl_buffer.
+ *
+ * Placing the forward declaration here means it comes before we
+ * #include cogl-winsys-egl-feature-functions.h bellow which
+ * declares lots of function pointers for accessing EGL extensions
+ * and cogl-winsys-egl.c will include this header before it also
+ * includes cogl-winsys-egl-feature-functions.h that may depend
+ * on this type.
+ */
+#ifdef EGL_WL_bind_wayland_display
+struct wl_resource;
+#endif
+
 typedef struct _CoglWinsysEGLVtable
 {
   CoglBool