Support for linking to glossary terms via URL hash

Re: Issue #[172](https://github.com/scala/scala.github.com/issues/172)

As suggested by @swartzrock, you could now link directly to the entry for "function literal" like this:
http://docs.scala-lang.org/glossary/#function-literal

It also fixes a (potential future) issue where external links in the glossary would not have worked, since all `<a>` elements had their default prevented, so I've limited this behaviour to `<a href="#...">` elements.