Fix for a name collision.  Older versions of GLib didn't have a function for inserting an item at an arbitrary position in a GPtrArray, so this file contains one.  But GLib introduced a function to do this in v2.40.  The function in this file (now named ptr_array_insert) can be deleted once GLib 2.40 is available for win32.  The highest version available for win32 at this time is 2.34.