Add g_list_store_sort

GListStore already has a g_list_store_insert_sorted function,
which can be used to keep the list sorted according to a fixed
sort function. But if the sort function changes (as e.g. with
sort columns in a list UI), the entire list needs to be
resorted. In that case, you want g_list_store_sort().

https://bugzilla.gnome.org/show_bug.cgi?id=754152

docs/reference/gio/gio-sections.txt

@@ -4443,6 +4443,7 @@ g_list_store_append
 g_list_store_remove
 g_list_store_remove_all
 g_list_store_splice
+g_list_store_sort
 <SUBSECTION Standard>
 G_TYPE_LIST_STORE
 <SUBSECTION Private>