I think I've found the solution. Please consider this patch: 

===
modified file 'lisp/ChangeLog'
--- lisp/ChangeLog 2012-07-06 13:50:37
+0000
+++ lisp/ChangeLog 2012-07-06 07:08:10 +0000
@@ -1,11 +1,3
@@
-2012-07-06 Toon Claes <toon@tonotdo.com>
-
- * progmodes/cc-fonts.el
(gtkdoc-font-lock-keywords):
- Less restrictive checking for gtkdoc.
-
-
* progmodes/cc-vars.el: For c++-mode set gtkdoc the default
-
c-doc-comment-style.
-
 2012-07-06 Glenn Morris <rgm@gnu.org>

 *
Makefile.in (compile-one-process): Rename from "recompile".

===
modified file 'lisp/progmodes/cc-fonts.el'
---
lisp/progmodes/cc-fonts.el 2012-07-06 13:50:37 +0000
+++
lisp/progmodes/cc-fonts.el 2012-01-19 07:21:25 +0000
@@ -2572,7 +2572,7
@@

 (defconst gtkdoc-font-lock-keywords
 `((,(lambda (limit)
-
(c-font-lock-doc-comments "/\*\*\([^\*/].*\)?$" limit
+
(c-font-lock-doc-comments "/\*\*$" limit

gtkdoc-font-lock-doc-comments)
 (c-font-lock-doc-comments "/\*< " limit

gtkdoc-font-lock-doc-protection)

=== modified file
'lisp/progmodes/cc-vars.el'
--- lisp/progmodes/cc-vars.el 2012-07-06
13:50:37 +0000
+++ lisp/progmodes/cc-vars.el 2012-02-11 22:13:29
+0000
@@ -552,8 +552,7 @@
 (defcustom-c-stylevar c-doc-comment-style

'((java-mode . javadoc)
 (pike-mode . autodoc)
- (c-mode . gtkdoc)
-
(c++-mode . gtkdoc))
+ (c-mode . gtkdoc))
 "*Specifies documentation
comment style(s) to recognize.
 This is primarily used to fontify doc
comments and the markup within
 them, e.g. Javadoc comments.
@@ -563,7
+562,7 @@

 javadoc -- Javadoc style for "/** ... */" comments (default
in Java mode).
 autodoc -- Pike autodoc style for "//! ..." comments
(default in Pike mode).
- gtkdoc -- GtkDoc style for "/** ... **/"
comments (default in C/C++ mode).
+ gtkdoc -- GtkDoc style for "/** ...
**/" comments (default in C mode).

 The value may also be a list of doc
comment styles, in which case all
 of them are recognized simultaneously
(presumably with markup cues