More structure.xml fixes

With this, as before:
- ```@link```, ```@see``` and their derivatives generate a "link" attribute.
- ```@version``` and its derivatives have the version vector prepended to the description.

(both of these affect legacy templates like new-black for example)

EDIT: Also added links to type tags and changed htmlspecialchars() to just a str_replace() of "&". Otherwise, the descriptions end up containing stuff like "\&quot;".