Show user names as subpages of special pages in autocomplete search

Show user names as subpages of special pages in autocomplete search

The autocomplete search allows special pages to define the list of
subpages to be excepted. Use user names on the following special pages,
because these special pages can be called with a user name as subpage.

Special:Block
Special:Contributions
Special:DeletedContributions
Special:Emailuser
Special:Listfiles
Special:Unblock
Special:Userrights

This makes it easier to navigate to this special pages with a prefilled
user name field.

Hidden user names are always not shown, because the suggestion is cached
between priviliged user and non-priviliged user.

Change-Id: I7db575bf66caaa5136489ed99f1655673b55adaf