Cleanups: fix deprecated g_type_class_add_private()

- use G_DECLARE_ and G_DEFINE_ macros
- move all data into ClassNamePrivate
- use _get_instance_private()

This should not introduce any functional changes or breakage.

Skipped two classes (EekKeyboard and EekboardContextService) for now in
order not to break the build.

These two classes are used in some very funky WIP code that tries to
circumvent encapsulation.

(Funky code is in eekboard/key-emitter.c and eekboard/eekboard-context-service.c)

eek/eek-container.h

@@ -30,14 +30,7 @@
 G_BEGIN_DECLS
 
 #define EEK_TYPE_CONTAINER (eek_container_get_type())
-#define EEK_CONTAINER(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), EEK_TYPE_CONTAINER, EekContainer))
-#define EEK_CONTAINER_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), EEK_TYPE_CONTAINER, EekContainerClass))
-#define EEK_IS_CONTAINER(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), EEK_TYPE_CONTAINER))
-#define EEK_IS_CONTAINER_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), EEK_TYPE_CONTAINER))
-#define EEK_CONTAINER_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), EEK_TYPE_CONTAINER, EekContainerClass))
-
-typedef struct _EekContainerClass EekContainerClass;
-typedef struct _EekContainerPrivate EekContainerPrivate;
+G_DECLARE_DERIVABLE_TYPE (EekContainer, eek_container, EEK, CONTAINER, EekElement)
 
 /**
  * EekCallback:
@@ -50,14 +43,6 @@ typedef struct _EekContainerPrivate EekContainerPrivate;
 typedef void (*EekCallback) (EekElement *element, gpointer user_data);
 typedef gint (*EekCompareFunc) (EekElement *element, gpointer user_data);
 
-struct _EekContainer
-{
-    /*< private >*/
-    EekElement parent;
-
-    EekContainerPrivate *priv;
-};
-
 /**
  * EekContainerClass:
  * @foreach_child: virtual function for iterating over the container's children