D13394: C++: update for c++20 and fix some syntax errors

[jonathan poelen]

jpoelen edited the summary of this revision.
jpoelen added a reviewer: dhaumann.

REPOSITORY
  R216 Syntax Highlighting

REVISION DETAIL
  https://phabricator.kde.org/D13394

To: jpoelen, dhaumann
Cc: kde-frameworks-devel, michaelh, ngraham, bruns