(bug 44111) ErrorPageError log messages should be in English

We want log messages to be in English. ErrorPageError, however, will log
the messages using the language of the current user. This isn't often
noticed, because the normal page view code path doesn't log
ErrorPageError and the API doesn't usually have ErrorPageError thrown in
the first place.

The fix is simple enough: in the constructor, create a new Message
object and call ->inLanguage( 'en' ) on it. And, for good measure,
->useDatabase( false ) so customizations on the local wiki won't show up
in the log files either.

Since ErrorPageError already overrides report(), that will take care of
still showing the expected language to the end user.

Bug: 44111
Change-Id: I9a6ab43d63e76fa9708b62e32ddc3262aff282f7