[gtkmm] Finding file's mime type

[Veiko Sinivee <veiko sinivee solo delfi ee>]

Hi all,

I'm searching for a (portable) way to find a files mime type.
I could dig into /etc/mime.types but that's not portable. I have
developed an app using gtkmm. I found no way to get it from gtkmm.
I suppose it should be in the Gtk::Fileselection ? I found that GTK+
has a GtkFileInfo struct, but how to get it? Perhaps the
filechooser should return it. Anyways I found there is a headerfile
xgdmime.h with the exact function that I need:
const char *xdg_mime_get_mime_type_for_file(const char *file_name);
But I couldn't find this header from an installed system with
GTK+ 2.x and GTKMM 2.4. 
I'd like to use some GTK+ or GTKmm method to find this info
because I hope to keep my app portable to Linux & win32.
So how should one find the mime type?

regards,

Veiko