Semantic: headers available in multiple modes

[Miguel Guedes]

How can semantic be set up so as to allow a header be made available in 
multiple modes?

For instance, how can (/usr/include/glib-2.0/) glib.h be made available 
in both c-mode as well as c++-mode?

I've the following lines in the el source executed at startup by .emacs:

(semantic-add-system-include "/usr/include/glib-2.0/" 'c++-mode)
(semantic-add-system-include "/usr/include/glib-2.0/" 'c-mode)
(semantic-add-system-include "/usr/include/glibmm-2.4/" 'c++-mode)

...and am trying to allow glib's headers to be available in both c and 
c++ modes. But am failing.

How can it be done?

Many thanks!

--------------
 Further info

In c-mode, semantic-c-describe-environment gives:

Include Path Summary:

  This file's system include path is:
    /usr/include
    /usr/lib/gcc/x86_64-linux-gnu/4.6/include/
    /usr/local/include/
    /usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/
    /usr/include/x86_64-linux-gnu/
    /usr/include/


In c++-mode, semantic-c-describe-environment gives:

Include Path Summary:

  This file's system include path is:
    /usr/include/boost/
    /usr/include/glib-2.0/
    /usr/include/glibmm-2.4/
    /usr/include/gtk-3.0/
    /usr/include/gtkmm-3.0/
    /usr/include/libxml++-2.6/
    ~/prj/gtk-e/
    /usr/include/c++/4.6/
    /usr/include/c++/4.6/x86_64-linux-gnu/
    /usr/include/c++/4.6/backward/
    /usr/lib/gcc/x86_64-linux-gnu/4.6/include/
    /usr/local/include/
    /usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/
    /usr/include/x86_64-linux-gnu/
    /usr/include/