Registers code to be called when a thread is created. The form of the code is:
void function(QThread *);
void Object::member(QThread *);
The most common is a member function as this can be in some arbitrary object instance, thus making finding your data much easier. If
inThread is true, the upcall is made just after setting up the new thread and just before waking the thread who called
start() if it requested to wait. If it's false, the upcall is made just after the thread has been successfully started.
