Some items to fix:

- Fix a 'NULL' object to use for converting too/from null/undefined.
- Add a class, perhaps Server, were we can put custom functions.
- Add C-level to bind a Pike-function to the above class. Would be
  by modules and the core to add JS-level functions.
- Fix a wrapper for JS_TYPE_BUILTIN (NJS class/object). Unclear
  exactly how this could be done.

