A little code correction for the SplashScreen class

Hello Julian.

Under Windows, please, replace the code in the SplashScreen::show(…) function

from this:

addToDesktop (useDropShadow ? (ComponentPeer::windowAppearsOnTaskbar | ComponentPeer::windowHasDropShadow) : ComponentPeer::windowAppearsOnTaskbar);

to this one:

this will prevent a splash screen window from appearing on the taskbar. I think it is the more natural behaviour for splash screens.

Ok, sounds reasonable to me.