add a get_indices_with_depth method to GtkTreePath with proper GI array annotations

* get_indices does not return a length so we can not annotate it to return an
  array in bindings that use GObject Introspection
* this method is the same as get_indices except it takes an int * as the depth
  parameter which we can then use in the array annotation
* in C this function returns an integer pointer array and updates depth to the
  number of integers in the array
* in a GI binding this returns the native array type for the bound language
  (e.g. in PyGI this returns a list of integers)

docs/reference/gtk/gtk-sections.txt

@@ -4675,6 +4675,7 @@ gtk_tree_path_append_index
 gtk_tree_path_prepend_index
 gtk_tree_path_get_depth
 gtk_tree_path_get_indices
+gtk_tree_path_get_indices_with_depth
 gtk_tree_path_free
 gtk_tree_path_copy
 gtk_tree_path_compare

docs/reference/gtk/tmpl/gtktreemodel.sgml

@@ -412,6 +412,16 @@ compatibility reasons.
 @Returns: 
 
 
+<!-- ##### FUNCTION gtk_tree_path_get_indices_with_depth ##### -->
+<para>
+
+</para>
+
+@path:
+@depth: 
+@Returns: 
+
+
 <!-- ##### FUNCTION gtk_tree_path_free ##### -->
 <para>
 

gtk/gtk.symbols

@@ -4671,6 +4671,7 @@ gtk_tree_path_down
 gtk_tree_path_free
 gtk_tree_path_get_depth
 gtk_tree_path_get_indices
+gtk_tree_path_get_indices_with_depth
 gtk_tree_path_get_type G_GNUC_CONST
 gtk_tree_path_is_ancestor
 gtk_tree_path_is_descendant

gtk/gtktreemodel.c

@@ -622,6 +622,31 @@ gtk_tree_path_get_indices (GtkTreePath *path)
   return path->indices;
 }
 
+/**
+ * gtk_tree_path_get_indices_with_depth:
+ * @path: A #GtkTreePath.
+ * @depth: Number of elements returned in the integer array
+ *
+ * Returns the current indices of @path.
+ * This is an array of integers, each representing a node in a tree.
+ * It also returns the number of elements in the array.
+ * The array should not be freed.
+ *
+ * Return value: (array length=depth): The current indices, or %NULL.
+ *
+ * Since: 3.0
+ **/
+gint *
+gtk_tree_path_get_indices_with_depth (GtkTreePath *path, gint *depth)
+{
+  g_return_val_if_fail (path != NULL, NULL);
+
+  if (depth)
+    *depth = path->depth;
+
+  return path->indices;
+}
+
 /**
  * gtk_tree_path_free:
  * @path: A #GtkTreePath.

gtk/gtktreemodel.h

@@ -134,6 +134,10 @@ void         gtk_tree_path_prepend_index    (GtkTreePath       *path,
 					     gint               index_);
 gint         gtk_tree_path_get_depth        (GtkTreePath       *path);
 gint        *gtk_tree_path_get_indices      (GtkTreePath       *path);
+
+gint        *gtk_tree_path_get_indices_with_depth (GtkTreePath *path,
+						   gint        *depth);
+
 void         gtk_tree_path_free             (GtkTreePath       *path);
 GtkTreePath *gtk_tree_path_copy             (const GtkTreePath *path);
 GType        gtk_tree_path_get_type         (void) G_GNUC_CONST;