[Development] Abandoning fix for QTBUG-67970 - QString & std::u16string_view support

[Thiago Macieira]

Task filed by Herb Sutter.

https://bugreports.qt.io/browse/QTBUG-67970
https://codereview.qt-project.org/c/qt/qtbase/+/227684

There are conflicts in my rebase to 5.15 and I don't want to give the 
impression I'll have time to continue work. So just abandoning.

Someone else pick it up, please.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel System Software Products