[cpp-threads] Examples of cross-thread ordering

[Peter Dimov]

>>> Example 1:
>>>
>>>   // thread T1
>>>   x = 1; // a
>>>   y = 2; // b
>>>   r1 = y; // c

The interesting question here for me is whether b -> c under the C++MM 
because both operate on the same location y. Don't IA64 (ld.acq/st.rel), x86 
PO and TSO promise order in this case?