app, libgimp*, modules: don't use g_type_class_add_private() ...

... and G_TYPE_INSTANCE_GET_PRIVATE()

g_type_class_add_private() and G_TYPE_INSTANCE_GET_PRIVATE() were
deprecated in GLib 2.58.  Instead, use
G_DEFINE_[ABSTRACT_]TYPE_WITH_PRIVATE(), and
G_ADD_PRIVATE[_DYNAMIC](), and the implictly-defined
foo_get_instance_private() functions, all of which are available in
the GLib versions we depend on.

This commit only covers types registered using one of the
G_DEFINE_FOO() macros (i.e., most types), but not types with a
custom registration function, of which we still have a few -- GLib
currently only provides a (non-deprecated) public API for adding a
private struct using the G_DEFINE_FOO() macros.

Note that this commit was 99% auto-generated (because I'm not
*that* crazy :), so if there are any style mismatches... we'll have
to live with them for now.

app/display/gimptoolcompass.c

@@ -169,7 +169,8 @@ static void     gimp_tool_compass_update_angle    (GimpToolCompass        *compa
                                                    gboolean                flip);
 
 
-G_DEFINE_TYPE (GimpToolCompass, gimp_tool_compass, GIMP_TYPE_TOOL_WIDGET)
+G_DEFINE_TYPE_WITH_PRIVATE (GimpToolCompass, gimp_tool_compass,
+                            GIMP_TYPE_TOOL_WIDGET)
 
 #define parent_class gimp_tool_compass_parent_class
 
@@ -273,16 +274,12 @@ gimp_tool_compass_class_init (GimpToolCompassClass *klass)
                                    g_param_spec_double ("unit-angle", NULL, NULL,
                                                         -G_PI, G_PI, 0.0,
                                                         GIMP_PARAM_READABLE));
-
-  g_type_class_add_private (klass, sizeof (GimpToolCompassPrivate));
 }
 
 static void
 gimp_tool_compass_init (GimpToolCompass *compass)
 {
-  compass->private = G_TYPE_INSTANCE_GET_PRIVATE (compass,
-                                                  GIMP_TYPE_TOOL_COMPASS,
-                                                  GimpToolCompassPrivate);
+  compass->private = gimp_tool_compass_get_instance_private (compass);
 
   compass->private->point = -1;
 }