We've always had 'age' in events but it's never really been an
accurate representation of the event's age because we never did
anything with it. This transforms it into a local clock timestamp
when the event arives and when it comes out of the sync store, and
changes getLocalAge() to use it.
react-sdk doesn't appear to use getLocalAge() but any 3rd party apps
that do may notice a slight change in bahaviour.
David Baker
d77af1e67a