Use std::atomic_int for hsSafeRefCnt, and move it to hsRefCnt.h/cpp
Merge pnUtRef with hsRefCnt, and remove the former
pnUtRef started at zero refs instead of one, and this is simpler
than finding and removing all the extra Ref() calls.
More std::atomic and friends
Merge pull request #422 from zrax/atomics_n_refs

Use C++11 Atomics and merge duplicate RefCount implementations