Fix Special:Checkuser for log entries pointing to special pages

Right now Special:Checkuser treats all log entries which point to a
special page as ancient log entries. That's incorrect for various
log entries produced by extensions as eg. the AbuseFilter extension
links Special:Abusefilter as target. That led to rows on the CheckUser
special page which started like (log-name-8), see:
http://img541.imageshack.us/img541/1009/specialcheckuserlogentr.png

Due to this I've removed the code for ancient log entries as it's no
longer needed.

Change-Id: I9caab05835b7f7468b3179c5537158dbc3a50c9a
Merge "Fix Special:Checkuser for log entries pointing to special pages"