Adds title attribute to TOC links.

The title helps differentiating same name symbols in the TOC, especially
when they are heavily overloaded like in the system module.
Removes the last pragma from proc like types.
Adds plain symbol hrefs for human readable hyperlinks.
Adds itemSymOrID for human readable toc hyperlinks.
Makes symbol extraction not depend on visibility token.

The visibility token doesn't exist on doc2 phases, and therefore symbols
were being recorded as empty.
Adds itemSymOrID for overloaded symbols.

This is far from the ideal unique signature, but much better than a raw
numerical index.
Adds quoted variables for valid URLs.