Incorrect link on notifications emails

When Drupal has not been installed on the root directory, the notification emails that are sent to project 'owners' contain invalid links because it does not recognise the sub-directory.

eg
Click to view : http://www.example.com/node/4
Click to edit : http://www.example.com/node/4/edit

should be

Click to view : http://www.example.com/subdirectory/node/4
Click to edit : http://www.example.com/subdirectory/node/4/edit