message: remove QSignalMapper. Use lambda func instead.
diff: -#include <QSignalMapper>
  #include <QMessageBox>
  #include <QSettings>
  #include <QApplication>
  FontsPage::FontsPage(QWidget *parent) : TabPage(parent), m_ui(new Ui::FontsPage){
  m_ui->setupUi(this);
  - QSignalMapper *mapper = new QSignalMapper(this);
  - mapper->setMapping(m_ui->changeGeneralFontButton, m_ui->generalFontLabel);
  - mapper->setMapping(m_ui->changeFixedWidthFontButton, m_ui->fixedFontLabel);
  - connect(m_ui->changeGeneralFontButton, SIGNAL(clicked()), mapper, SLOT(map()));
  - connect(m_ui->changeFixedWidthFontButton, SIGNAL(clicked()), mapper, SLOT(map()));
  - connect(mapper, SIGNAL(mapped(QWidget*)), SLOT(onFontChangeRequested(QWidget*)));
  + connect(m_ui->changeGeneralFontButton, &QToolButton::clicked, [this](){onFontChangeRequested(m_ui->generalFontLabel);});
  + connect(m_ui->changeFixedWidthFontButton, &QToolButton::clicked, [this](){onFontChangeRequested(m_ui->fixedFontLabel);});
  readSettings();
  //icons
  