Fix loss of precision warnings

Found by http://www.viva64.com/en/b/0251

Change-Id: I2a0c3dba74fef07c3119c9e57b343a8253ee7daa
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Account for the sort indicator being placed above the text on Vista

In WindowsVista style and later the sort indicator is placed above the
text as opposed to alongside it. Therefore the extra space given is moved
to the common style allowing styles that have it placed differently to
easily ensure it is not included.

Task-number: QTBUG-19915
Change-Id: Ic21fcc1d95f4c3cc2eb9c465e1c8afb9b805389a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Cocoa: Make sure modal windows get correct geometry on show

beginModalSessionForWindow will center the window and ignore
the set geometry. So to workaround this it checks the new value
against the old one and moves it back if need be.

Change-Id: I38bc74c04138992f2e0570fca666414025aeeba8
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>