Add it to configure.json and replace all occurrences of QT_NO_THREAD
with QT_CONFIG(thread). Add conditions for other features that depend
on thread support. Remove conditions where we can use the QMutex and
QThreadStorage stubs.
Change-Id: I284e5d794fda9a4c6f4a1ab29e55aa686272a0eb
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>