Wrong multiplier was used for the most significant byte. Fix it even though it doesn't risk to be a problem in practice as the images of such gigantic size would surely break some limit anyhow. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66847 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775