[WIN32SS?] Opera 12.18 window maximized should not have a border

r74175 gcc dbg

Startup Opera 12.18 from rapps and maximize its window.
The maximized Window should have no border drawn as in
2K3-DoesNotHaveThatBorder.png

On ros it draws a border (esp. top & left) leading to the "closing-x" being drawn cut-off.
r74175-OperaMaximized-WeDontWantThatBorder.png

This happens in all three cases:
A themesvc running, classic theme selected (attached pic)
B themesvc deactivated, restarted, classic theme selected
C themesvc running, lautus selected

I reg-tested a bit and this is broken since ages: r65495 is affected as well.