Mainly:
* QSignalMapper -> connections with lambdas
* QRegExp -> QRegularExpressions (still some occurrences)
* QString::null -> QString::isNull()

Needs version check:
* QFontMetrics::width() -> QFontMetrics::horizontalAdvance() introduced in 5.11
* QTextEdit::setTabStopWidth() -> QTextEdit::setTabStopDistance introduced in 5.10