Fix the "you are now logged in/out" warning

It would tell you you were logged out when you were actually
logged in, and when I looked into it, I found lots of broken
things, including lots of confusion between the current
anon-ness and username and the new anon-ness and username.

ve.init.mw.Target:
* Check the new isAnon value, not the old one
* Pass the username to the event, rather than just anon-ness

ve.init.mw.ViewPageTarget:
* Use the passed username (new username) rather than the
  username from mw.config (which is updated, but confusing)

Change-Id: Icf406d49100d81e87c677fd6b57ff93cc29f601f
Merge "Fix the "you are now logged in/out" warning"