QT_USE_FAST_CONCATENATION doesn't do anything nowadays.
Using QT_USE_QSTRINGBUILDER is the same as QT_USE_FAST_OPERATOR_PLUS
for QStrings and enables more QStringBuilder use for QByteArrays.
Change-Id: Ibd297817c50d86661d47822799f989447249af1b
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Do not remove QT_USE_FAST_OPERATOR_PLUS and QT_USE_FAST_CONCATENATION
in QtcAutotest, but in the two tests that won't build with it.
In the qmake build the defines are not removed from json.pro, because
this file does not include qttest.pri.
Change-Id: I97d173528ca2a02bac1bfae30709a959e6b69375
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
