so-5.5.1: Two new methods for changing an agent state

Two new methods for changing agent's state are added in v.5.5.1.

First one uses new so_5::rt::state_t::activate() method. It means that agent's state can be changed this way:

class my_agent_t : public so_5::rt::agent_t
{
  const so_5::rt::state_t st_normal = so_make_state();
  const so_5::rt::state_t st_busy = so_make_state();
...
public :
  virtual void so_define_agent() override
  {
    st_normal.activate();
    ...
  }

  void evt_request( const msg_start_request & evt )
  {
    st_busy.activate();
    ...
  }

  void evt_complete_request( const msg_processing_result & evt )
  {
    ...
    st_normal.activate();
  }
};

The second one uses overloaded >>= operator:

class my_agent_t : public so_5::rt::agent_t
{
  const so_5::rt::state_t st_normal = so_make_state();
  const so_5::rt::state_t st_busy = so_make_state();
...
public :
  virtual void so_define_agent() override
  {
    this >>= st_normal;
    ...
  }

  void evt_request( const msg_start_request & evt )
  {
    this >>= st_busy;
    ...
  }

  void evt_complete_request( const msg_processing_result & evt )
  {
    ...
    this >>= st_normal;
  }
};

The old method so_5::rt::agent_t::so_change_state() is still here. It is not deprecated and will be supported by the future versions of SObjectizer. New methods are introduced to allow a developer to write more concise and readable code.