Custom code highlighting (BB-8029)

At https://bitbucket.org/kbecker/pshdl/wiki/tutorial\\
I want to document my own programming language. Unfortunately I can not get any useful syntax highlighting done. The problem is that if I don't specify any language, it is guessed. This means that something wrong is guessed as this language is not known to pygments yet. Unfortunately I also can not create my own <pre> blocks or other formatting options like span.
It would be awesome to:

• attach custom CSS and styles to code
• disable the automatic language guessing

Karsten