private boolean isSubjectChangeStrict() {
        return JiveGlobals.getBooleanProperty("xmpp.muc.subject.change.strict", true);
    }
Returns true if the given message qualifies as a subject change request for
the target MUC room, per XEP-0045. Note that this does not validate whether 
the sender has permission to make the change, because subject change requests
may be loaded from history or processed "live" during a user's session.

Refer to http://xmpp.org/extensions/xep-0045.html#subject-mod for details.

@param message the message to check
@return true if the given packet is a subject change request
xmppserver/src/main/java/org/jivesoftware/openfire/muc/HistoryStrategy.java