How to create a new directory?

[Gerardo Ballabio <gerardo ballabio gmail com>]

Hi all,
can you please tell me what is the recommended and most portable way
to create a new directory in a gtkmm program?

Browsing the glibmm documentation I didn't found any interface for
creating a new directory.  If I read correctly, class Glib::Dir
provides a read-only interface that only allows to read existing
directories.

I want specifically to create a directory where to store user-specific
data for a game (configuration settings, scores etc.).  Functions like
Glib::get_user_config_dir and Glib::get_user_data_dir return suggested
paths where to store application data (on my Debian system they are
$HOME/.config and $HOME/.local/share respectively), but most
applications don't write their files directly there: rather, they
create their own subdirectories.  I want to do the same.

I might use the Unix mkdir system call, but then my program wouldn't
be portable to non-Unix systems.  Is there a more general solution?

Thanks in advance
 Gerardo