* This commit is half-revert, half-rewrite. It reverts the board status icon functionality to 'unread posts', as it was originally, but: (1) actually fixes it, (2) provides the exact number of unread posts, and (3) only cares about messages sent after *after* your last visit (which, incidentally, makes the SQL query viable). This also allows me to remove the various .age-* classes, which was getting confusing. Simplicity is best. (Subs-BoardIndex.php, Subs.php, Boards.template.php, MessageIndex.template.php, sections.css)

* Mobile skins (Wireless and Wilderless) will now be more accommodating with board status icons, and show them in the regular flow, rather than their own table cell. (Boards.template.php, MessageIndex.template.php)