Changes between glibmm 2.2 (previously part of gtkmm) and glibmm 2.4:

* glibmm is now a separate module, for use with non-GUI software.
  (Note that glibmm 2.4 and gtkmm 2.4 install in parallel with
   gtkmm 2.2 - so you can install and use both simultaneously and
   port to 2.4 whenever you are ready.) 
* glibmm now uses libsigc++ 2 rather than libsigc++ 1.2.
  There is a libsigc++ compatibility header. The new, undeprecated, API
  is slightly improved.
  - Connecting signal handlers:
      signal_something().connect( SigC::slot(*this, &Something::on_something) );
    should become
      signal_something().connect( sigc::mem_fun(*this, &Something::on_something) );
    or, for non-member methods:
      signal_something().connect( sigc::ptr_fun(&Something::on_something) );
  - Binding extra parameters:
      SigC::bind(...)
    should become
      sigc::bind(...)
  - Declaring signals:
      SigC::Signal1<void, int>
    should become
      sigc::signal<void, int>
  - Declaring slots:
      SigC::Slot1<void, int>
    should become
      sigc::slot<void,int>
  - Inheriting from the libsigc++ base class:
      class Something : public SigC::Object
    should become
      class Something : public sigc::trackable