2.3.1:

* gmmproc changes needed by gtkmm 2.3.0
  (Murray Cumming)
* examples updated and buildable and working,
  without gtkmm code.
  (J. Abelardo Gutierrez)

Changes in glibmm 2.3.0:

* Now separate from gtkmm, so you can use things like Glib::ustring without depending on gtkmm.
  This glibmm 2.4 API installs in parallel with gtkmm 2.0/2.2, so you can install this unstable library 
  without the risk of breaking existing application.
* This does not yet require glib 2.3 because there has been no tarball release of that yet. For now, you
  can use glibmm 2.3.0 with glib 2.2.x.
* When using pkg-config, you should check for "glibmm-2.4".
* Glib::ObjectBase inherits virtually from SigC::Object, allowing multiple inheritance with other
  classes that inherit from SigC::Object.
* RefPtr:
  - is_null() was removed, to encourage you to use "== 0" instead.
  - operator=(CppObject*) was removed.
* gtkmmproc is now gmmproc.
* All the glibmm bugfixes in gtkmm 2.2.x.
