Windows native file dialog: Work around display bug of IFileDialog.

Any filter not filtering on suffix shows up duplicated in filter
combo.

Change-Id: I9fc9e33b6081cf6894fabc6dd52c12a4d3dfd393
Task-number: QTBUG-42405
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>
Windows: fix unreadable white text for focused combo boxes

Task-number: QTBUG-42390
Change-Id: Ia52c7ac3d2e3ca155692c8f020a565054716c86b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Skip unused function isCoreProfile() on non-ES2 platforms

Change-Id: Ia84e74512e7001986c620253cdf0bc431ebc00dc
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>