Simple, and first implementation to Yii translation fallback before raise a CMissingTranslationEvent. ex. from 'pt_PT', fallback to 'pt' and only then raise event if not found

CMessageSource.php

protected function translateMessage($category,$message,$language)
{
	$key=$language.'.'.$category;
	if(!isset($this->_messages[$key]))
		$this->_messages[$key]=$this->loadMessages($category,$language);
	if(isset($this->_messages[$key][$message]) && $this->_messages[$key][$message]!=='')
		return $this->_messages[$key][$message];
                
    // testing fallback translation language. ex. 'pt' instead of 'pt_PT'
    if (strlen($language) === 5) {
        $key = substr($language, 0, 2) . "." . $category;
                    
        $this->_messages[$key] = $this->loadMessages($category, substr($language, 0, 2));
                    
        if(isset($this->_messages[$key][$message]) && $this->_messages[$key][$message]!=='')
            return $this->_messages[$key][$message];                    
    }
    // end of testing
            
	elseif($this->hasEventHandler('onMissingTranslation'))
	{
		$event=new CMissingTranslationEvent($this,$category,$message,$language);
		$this->onMissingTranslation($event);
		return $event->message;
	}
	else
		return $message;
}

code between '//testing ...' and '// end of testing' was only thing added to original method, nothing more was changed.

take in consideration that testing was only conducted agains php files translation, not tested agains DbMessage translations etc etc..