Dropped direct globals from fileDownloadFormatTime().

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5403 2fea6a4d-a838-0410-917b-93a53c48e9d2
Dropped references to $prefs from get_lastmod().

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5404 2fea6a4d-a838-0410-917b-93a53c48e9d2
Dropped references to $prefs from handle_lastmod().

This also fixes the unintentional variable overwrite that
could happen due to extraction of $prefs global.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5405 2fea6a4d-a838-0410-917b-93a53c48e9d2