make warnWeightCnt static std::atomic<bool>
use compare_exchange_strong
Merge pull request #1438 from gartung/statics-SimCalorimetry-EcalSelectiveReadoutProducers

Multithreading fixes -- make warnWeightCnt static std::atomic<bool>
Merge remote-tracking branch 'origin/CMSSW_7_0_X' into CMSSW_7_0_X