code: function move_aspirate_forward(hash) {
      var asp = u.unasp2asp(hash.stemUlt);
      if (!asp) return;
      var stem = u.replaceEnd(hash.stem, hash.stemUlt, asp);
      if (!stem || stem == hash.stem) return;
      hash.stems = [stem];
      if (debug) log('mod: move_aspirate_forward', stem);
  }
docs: t- and th-, when they are the second letter, become dh-