[cogl-handle] Optimize how we define cogl handles

The cogl_is_* functions were showing up quite high on profiles due to
iterating through arrays of cogl handles.

This does away with all the handle arrays and implements a simple struct
inheritance scheme. All cogl objects now add a CoglHandleObject _parent;
member to their main structures. The base object includes 2 members a.t.m; a
ref_count, and a klass pointer. The klass in turn gives you a type and
virtual function for freeing objects of that type.

Each handle type has a _cogl_##handle_type##_get_type () function
automatically defined which returns a GQuark of the handle type, so now
implementing the cogl_is_* funcs is just a case of comparing with
obj->klass->type.

Another outcome of the re-work is that cogl_handle_{ref,unref} are also much
more efficient, and no longer need extending for each handle type added to
cogl. The cogl_##handle_type##_{ref,unref} functions are now deprecated and
are no longer used internally to Clutter or Cogl. Potentially we can remove
them completely before 1.0.

gl/cogl-shader-private.h

@@ -26,11 +26,13 @@
 #ifndef __COGL_SHADER_H
 #define __COGL_SHADER_H
 
+#include "cogl-handle.h"
+
 typedef struct _CoglShader CoglShader;
 
 struct _CoglShader
 {
-  guint              ref_count;
+  CoglHandleObject   _parent;
   GLhandleARB        gl_handle;
 };