The `slideshow/code-pict' library is the same as `slideshow/code', but
it works in non-GUI settings. Only the `slideshow/code' library connects
the code font size to `current-font-size', though.
The `code' macro, `define-code', etc., now support "code transformers",
which are syntax bindings that trigger otherwise-unescaped transformations
in the code to typeset (which can make the code easier to read and
friendlier to auto-indentation).
