The certificate of incorporation of any corporation may provide that in all elections of directors of such corporation each shareholder shall be entitled to as many votes as shall equal the number of votes which, except for such provisions as to cumulative voting, he would be entitled to cast for the election of directors with respect to his shares multiplied by the number of directors to be elected, and that he may cast all of such votes for a single director or may distribute them among the number to be voted for, or any two or more of them, as he may see fit, which right, when exercised, shall be termed cumulative voting.