hst:include statements in freemarker do not work on Weblogic

HST response states can be nested. This is the case when including fragments for instance with hst:include tags. In these cases the parent state might be using a writer, while the child state is using an output stream. When the child state is flushed, it sees that it is using an output stream but then erroneously (and unjustifiably) assumes the parent is using an output stream too. At that moment it tries to use the parent's output stream, but since the parent was using a writer it will throw an illegal state exception. The hst response state must be modified to handle such cases where the parent state is using a different output method than the child.