missing atomics in node bitmap update

[tromp]

The following pragmas avoid losing some set bits when multiple threads race to set a bit in the same word. There is still a risk of two threads trying to set the exact same bit and both seeing it 0 before the update, but that's less likely (an issue that cuckatoo avoids).

			// Two bit counter for cuckoo
			if ((bucketNodes[targ] & one) != 0) {

•   			#pragma omp atomic update
    			bucketNodes[nodesPerBucket + targ] |= one;
    		}
  

•   		#pragma omp atomic update
    		bucketNodes[targ] |= one;