Draft: Address #68: Add syntax highlighting of examples to cmucl internals
We add syntax highlighting of examples to the cmucl internals manual.
Syntax highlighting is done using highlight js and is set in docs/texi2html.init. This supports highlighting things in @lisp and @example.
Also, we add some CSS to add a background color to examples to set up the example code from the surrounding text. This is modeled after the emacs manual.
We also add the background color to verbatim blocks.