As many people already discovered, it seems to be impossible to compile the Qt library with WebKit when using the MS Visual Studio 2008 compiler.
Only running configure with -no-webkit let the compiler complete its work without error. This results in a Qt library without WebKit of course, but that is no problem if you don't need WebKit.

As I just read on the following page (http://webkit.org/building/tools.html) WebKit supports Visual Studio up to version 2005, but not newer versions.
So if you rely on WebKit and want to use VS 2008: Tough luck!

If anyone managed to compile Qt with WebKit and VS 2008 the solution would be most welcome here.