Improved personal toolbar for logged-out users

Improved personal toolbar for logged-out users

Previously, logged-out users either only saw "Create account" and "Log in"
links in the personal area, or if $wgShowIPinHeader was true, they saw

  [icon] 127.0.0.1  Talk for this IP address  Create account  Log in

where the IP address itself linked to the IP user page.

Now, logged-out users by default see the following:

  [icon] Not logged in  Talk  Contributions  Create account  Log in

The old $wgShowIPinHeader feature is removed. It is very unfriendly to
show the user's IP address (in red, no less) at the top of every page,
since this will mean nothing to most visitors. Caching means that this
can't even be done reliably, anyway.

Another improvement is that the "talk" and "contributions" links are not
shown if anonymous users don't have the 'edit' right.

Modelled after the loggedOutTalkPage() function at Dutch Wikipedia
<https://nl.wikipedia.org/w/index.php?oldid=44706954>

Bug: T112724
Change-Id: I6f44e3e5d97ea917e4a03af47f3795792e4ca122