code: private int addWithClosure(CharSequence nfdPrefix, CharSequence nfdString,
                  long[] newCEs, int newCEsLength, int ce32) {
          // Map from the NFD input to the CEs.
          ce32 = addIfDifferent(nfdPrefix, nfdString, newCEs, newCEsLength, ce32);
          ce32 = addOnlyClosure(nfdPrefix, nfdString, newCEs, newCEsLength, ce32);
          addTailComposites(nfdPrefix, nfdString);
          return ce32;
      }
docs: Adds the mapping and its canonical closure.
  Takes ce32=dataBuilder.encodeCEs(...) so that the data builder
  need not re-encode the CEs multiple times.