Fix Qt dep warn and remove XLFD font workaround

Fix Qt dep warn and remove XLFD font workaround

This commit fixes a few warnings from Qt 5.14 regarding
QFont::setRawName() and QFont::rawName() like the following one:

  error: ‘void QFont::setRawName(const QString&)’ is deprecated [-Werror=deprecated-declarations]

These methods were deprecated in Qt 5.3. [1]

This commit removes code from 2002 (539ce478) that worked around a
problem in Qt's handling of XLFD fonts that no longer seems relevant
since XLFD is no longer supported in Qt 5 [2]. Even if the problem
were relevant, setRawName() would not fix anything since it is now
an empty method. [3]

I tested that compilation with Qt 4.8.7 works without error.

[1] https://code.qt.io/cgit/qt/qtbase.git/tree/dist/changes-5.3.0/?h=v5.14.0
[2] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=3a8d7b0b9a4db91415b7bda2582a59a76b3754dc
[3] https://codereview.qt-project.org/c/qt/qtbase/+/100292/