comments_open returns false on page

[TheTomThorogood]

The internal functions _close_comments_for_old_posts and _close_comments_for_old_post should check if there dealing with a page and if so return the old value instead of returning false if the page was published older then the threshold.

Neither _close_comments_for_old_post() nor _close_comments_for_old_posts() returns false on pages. It does no post type check at all, actually. They use the same settings as posts.