code: public static LongStreamEx constant(long value, long length) {
          return of(new ConstSpliterator.OfLong(value, length, false));
      }
docs: Returns a sequential unordered {@code LongStreamEx} of given length which
  elements are equal to supplied value.
  
  @param value the constant value
  @param length the length of the stream
  @return a new {@code LongStreamEx}
  @since 0.1.2