Remove org.jivesoftware.util.FastDateFormat

org.jivesoftware.util.FastDateFormat provides a thread safe (and presumably faster) equivalent to java.text.SimpleDateFormat. The implementation of FastDateFormat is pretty old, based on no longer available third-party code, and has arguable defects (eg: its Pair implementation’s inner compareTo assumes that the second argument is comparable, while it isn’t.

The benefits of FastDateFormat do no longer outweigh the added complexity of maintaining the code. It should be removed.