qt: fix signal-mapper deprecation warnings

I included adaptation here of a few existing cases using a different
solution to the helper defines suggested in review.

Example warning:
```
../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp: In constructor 'SPrefsCatList::SPrefsCatList(qt_intf_t*, QWidget*)':
WARNING : ../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp:254: 40:  'void QSignalMapper::mapped(int)' is deprecated: Use QSignalMapper::mappedInt(int) instead [-Wdeprecated-declarations]
  254 |     connect( mapper, QOverload<int>::of(&QSignalMapper::mapped), this, &SPrefsCatList::switchPanel );
      |                      ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/qt5/QtCore/QSignalMapper:1,
                 from ../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp:45:
/usr/include/x86_64-linux-gnu/qt5/QtCore/qsignalmapper.h:71:10: note: declared here
   71 |     void mapped(int);
      |          ^~~~~~
```