Show full hierarchy for classes (including non-Drupal classes)

Migrated issue

Reported by: jhodgdon

The API module has a nice hierarchy display at the top of class pages, but it doesn't show classes outside the scope of Drupal. For instance:

This class is defined as
abstract class DatabaseConnection extends PDO

but I can't tell that unless I scroll down to the bottom and view the code. I think it would be useful to display that at the top.