Fix warnings coming from deprecations of QTextEdit::tabStopWidth()
and QFontMetrics::width(). Regarding tabStopWidth(), the ChangeLog
states the following [1]:
Introduced tabStopDistance property in QTextOption, QTextEdit and
QPlainTextEdit as replacement for the inconsistently named tabStop and
tabStopWidth properties. QTextOption::tabStop, QTextEdit::tabStopWidth and
QPlainTextEdit::tabStopWidth are now deprecated.
Note that QFontMetrics::horizontalAdvance() is what we want here, as
opposed to QFontMetrics::boundingRect(), because we want to know
where to draw the next character after the tab.
[1] https://code.qt.io/cgit/qt/qtbase.git/tree/dist/changes-5.10.0/?h=v5.10.0
In particular, the directory frontends/qt4 is renamed to frontends/qt.
Many configurations file have to be updated. All mentions of qt4 in
the source have been audited, and changed to qt if necessary.
The only part that has not been updated is the CMake build system.
