(#3404) Stop type hinting with LeapExport, that class doesn't exist.
On PHP 5.1, this was causing a fatal error when it was hit. On PHP 5.2 or greater, this causes an E_RECOVERABLE_ERROR. Due to a bug in Mahara's error handler, such errors were being squashed so we never saw them. Whoops! Signed-off-by: Nigel McNie <firstname.lastname@example.org>