(decedent had been previously married and died with will executed during prior marriage which left property to spouse if spouse survived, then to children; decedent remarried and did not amend will to provide for current spouse (plaintiff); pre-marital agreement entered into specifying that plaintiff would receive none of decedent's assets held in revocable trust; plaintiff held to be pretermitted spouse entitled to intestate share of decedent's estate, but premarital agreement upheld).