[mythtv] keypressEvent improvement: Add actionEvent in mythuitype class

[Xavier Hervy]

I forgot the return value for actionEvent

bool MythUIButton::actionEvent(QString action)
{
    bool handled = false;
    if (action == "SELECT")
    {
        if (!IsEnabled())
            return false;

        if (m_Pushed)
            UnPush();
        else
            Push();
    }
    else
        handled = false;
    return handled;
}