Review use of multi thread semantics. Do we need to use C++11?

There are various multi threading patterns which frequently occur in our code, but there is often some confusion over whether critical sections/locks/memory barriers are required.

Some examples:

• Setting a boolean on one thread, and accessing from another. [And any reordering issues of code before/after]
• Incrementing a value from one thread and checking from another
• Decrementing a value from one thread and checking from another
• check boolean, get lock, check boolean again
• Reusing the same value set from another thread gives consistent values.

X86/64 is strongly ordered, but other platforms powerpc/arm may expose problems in the existing implementation.

One question is whether we need to switch to c++11 in order to obtain the necessary atomic memory ordering constraints.

jakesmith richardkchapman mckellyln for discussion...we should document best practice somewhere in the sources, and extend as we hit new examples.