new Version 3.0.5: replace exit()-call on broken pipe() with throwing YUIException()

YUI::topmostConstructorHasFinished() now throws a YUIException() instead of calling exit(), which gets rethrown by YUILoader::loadUI and ends up in the code from where the UI was initialized. This help finishing your prog in clean way, if you are using libyui with threads and pipe() to UI-plugin fails.