* (bug 11114) Fix regression in read-only mode error display during editing

* (bug 11114) Fix regression in read-only mode error display during editing
Regression caused by the new permissions error reporting system.
For read-only case, the read-only text didn't get passed back with the message from Title::getUserPermissionsErrors().
The text is either originally set in $wgReadOnly or gets loaded into it from $wgReadOnlyFile during wfReadOnly(), so pulling that it now gets passed back as expected.
Other functions using $wgOut->readOnlyPage() would have still got the original, still working, behavior.