nodeSetOp.c: missing additionalsize for BuildTupleHashTable().
Provide additionalsize argument, which can affect the calculations for
'nbuckets'. Also, future work for Hash Aggregation will rely on the
correct additionalsize.
Discussion: https://postgr.es/m/
7530bd8783b1a78d53a3c70383e38d8da0a5ffe5.camel%40j-davis.com