It shall be lawful for every person to devise, bequeath, or dispose of, by his will executed in manner herein-after required, all real estate and all personal estate which he shall be entitled to, either at law or in equity, at the time of his death, and which, if not so devised, bequeathed, or disposed of, would devolve . . . F1 upon his executor or administrator; and the power hereby given shall extend . . . F1 to all contingent, executory or other future interests in any real or personal estate, whether the testator may or may not be ascertained as the person or one of the persons in whom the same respectively may become vested, and whether he may be entitled thereto under the instrument by which the same respectively were created, or under any disposition thereof by deed or will; and also to all rights of entry for conditions broken, and other rights of entry; and also to such of the same estates, interests, and rights respectively, and other real and personal estate, as the testator may be entitled to at the time of his death, notwithstanding that he may become entitled to the same subsequently to the execution of his will.