comment start in cc-mode extension

[f00biebletch]

I am trying to write a major mode based on cc-mode for the Fan
programming language and need to support comments starting with "**"
and am having problems.  I've set the following variables to no avail:

(c-lang-defconst c-comment-start-regexp
;  fan "\\(\\(//+\\|/\\*+\\)\\|\\*\\*\\)\\s *")
  fan "\\(//+\\|/\\*+\\)\\|\\*\\*")

(c-lang-defconst c-block-comment-starter fan "**")
(c-lang-defconst c-block-comment-ender   fan "**")

(c-lang-defconst c-comment-start-regexp  fan "\\(//|\\*\\*\\)")
(c-lang-defconst c-block-comment-start-regexp fan "\\(/[*+]|\\*\\*\
\)")

I've also tried fandoc-font-lock-keywords and then adding fandoc to c-
doc-comment-style per the documentation on cc-mode, but that has not
worked either.

I'm pretty incompetent with lisp, and more so with cc-mode, so any
help would be appreciated.