Remove line breaks and indentation around links text: At least Chrome/Firefox on
Windows add the white space(s) from the HTML Code to the link text, which
results in "jumping" labels. The behaviour can be observed with the Hello Theme
while toggling the bookmark status.
Essentially, if an enclosure tag exists in the item, then the item menu will contain
a link 'multimedia [speaker symbol]' to the media url. Otherwise, if there is no
enclosure tag, there is no menu item shown.
This feature required adding an enclosure column to the items table (models/schema.php)
and bumping the DB version to 21 (models/config.php). I also added enclosure tag logic
to the Rss20 parser, the model/item.php and template/item.php files.
