winrtrunner: use HString class where appropriate

Change-Id: I9b56594b65a545ea98e033ec57788f51cfd6695d
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
qtd3dservice: use HString class where appropriate

Change-Id: Ia75e2dbda53229691b4d4bc58b2b4dec1f083256
Reviewed-by: Andrew Knight <andrew.knight@digia.com>