QTemporaryDir: Output warnings on removal failure.

Change-Id: I38d0a07c355f73899cc5f6eac60bd8cbedc73cb2
Reviewed-by: David Faure <david.faure@kdab.com>
Fix temporary file leak in tst_qfiledialog2.

Change-Id: I5a1e601e3aa6e84300efa09bfbd9232fecab903e
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>
Reviewed-by: David Faure <david.faure@kdab.com>