MinGW: Fix warnings about assigned but not used variables.

Change-Id: I114483273db0f9ffe0527b4a3e4cd881375a3448
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Fix MinGW-warnings about narrowing/invalid conversions.

Change-Id: I9b49dd6d12a5e59c6f2674ab3c82a8a7ec583775
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>