The second parameter of gtk_widget_set_realized is of type gboolean
(gint). This is to ensure compatibility on alternative compilers and
platforms.

This update replaces depreciated Gtk1.x symbols with Gtk2.x symbols in
preparation for adding Gtk3 support. These edits aim to be fully
compatible with Gtk2.x, allowing backward compatibility.

The following symbols have been replaced in this commit:

Gtk symbols that have been moved to the Gdk library:
 - GtkType -> Gtype
 - GTK_CHECK_CAST -> G_TYPE_CHECK_INSTANCE_CAST
 - GTK_CHECK_TYPE -> G_TYPE_CHECK_INSTANCE_TYPE
 - gtk_signal_connect -> g_signal_connect
 - GTK_SIGNAL_FUNC -> G_CALLBACK
 - gtk_type_class -> g_type_class_peek
 - gtk_type_new-> g_object_new
 - GtkTypeInfo -> GtypeInfo (Not required for
   g_type_register_static_simple)
 - gtk_type_unique -> g_type_register_static_simple
 - gdk_draw_image_rgb -> replaced by gdk_cairo_source_pixbuf
   NB: This requires porting to use cairo contexts and GdkPixbufs.

The following gtk symbols are changed for their modern equivalent:
 - GTK_WIDGET_REALIZED -> gtk_widget_get_realized
 - GTK_OBJECT_FLAGS -> gtk_widget_set_realized

Symbols without replacement:
 - gtk_range_set_update_policy -> No replacement; as default policy is
   set to continuous we can delete this line.

* removed OpenGLFuncTab, now extensions are loaded internally
* added support of GlBuffer and GlTexture2D to InputArray/OutputArray
* added ELEMENT_ARRAY_BUFFER and PIXEL_PACK_BUFFER targets
* added copyFrom/copyTo method for GlBuffer and GlTexture2D
* removed GlFont
* removed pointCloudShow
* removed OpenGLCleanCallback
* added Access parameter to GlBuffer::mapHost
* added autoRelease parameter to all create methods

* removed OpenGLFuncTab, now extensions are loaded internally
* renamed GlTexture -> GlTexture2D
* added support of GlBuffer and GlTexture2D to InputArray/OutputArray
* added ELEMENT_ARRAY_BUFFER and PIXEL_PACK_BUFFER targets
* added copyFrom/copyTo method for GlBuffer and GlTexture2D
* removed GlFont
* removed pointCloudShow
* removed OpenGLCleanCallback