[QtScript/JavaScriptCore] Fix tst_QScriptEngine::throwErrorFromProcessEvents

Patch: http://gitorious.org/+qtwebkit-developers/qtwebkit/qtwebkit-qtscript-integration/commit/d2e46389ae7aee02b76ab3d4f65bfb5cc57f4cf2

The issue here is that JSC doesn't expect didTimeOut() to throw an exception – but since we made it virtual, that can happen (since we call out to application code. which can do anything).

"while(true){}" is not a realistic script to be running. We could say that throwing an error due to processEvents() will not cause the script to abort in this case. But if arbitrary scripts can be provided by the user, this could be exploited...