Add temporary cogl-clutter.h to aid splitting out Cogl

This gives us a way to clearly track the internal Cogl API that Clutter
depends on. The aim is to split Cogl out from Clutter into a standalone
3D graphics API and eventually we want to get rid of any private
interfaces for Clutter so its useful to have a handle on that task.
Actually it's not as bad as I was expecting though.

cogl/cogl-clutter.h

@@ -0,0 +1,47 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2011 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
+#error "Only <cogl/cogl.h> can be included directly."
+#endif
+
+#ifndef __COGL_CLUTTER_H__
+#define __COGL_CLUTTER_H__
+
+#ifdef COGL_HAS_XLIB
+#include <X11/Xutil.h>
+#endif
+
+G_BEGIN_DECLS
+
+#define cogl_clutter_check_extension cogl_clutter_check_extension_CLUTTER
+gboolean
+cogl_clutter_check_extension (const char *name, const char *ext);
+
+#define cogl_onscreen_clutter_backend_set_size cogl_onscreen_clutter_backend_set_size_CLUTTER
+void
+cogl_onscreen_clutter_backend_set_size (int width, int height);
+
+G_END_DECLS
+
+#endif /* __COGL_CLUTTER_H__ */