为RSS feed图标改变alt和title属性

In D6 the alt attribute of the RSS feed icon themed by theme_feed_icon() was statically set to "Syndicate content" and the title attribute of the icon was set to the string passed to the function in the $title parameter.

Drupal 7 sets the alt attribute of the image and the title attribute of the anchor for the RSS feed to the same text. The text is comprised of "Subscribe to " + the $title string passed to theme_feed_icon().