A fix for tomath repr bitops

nqp_bigint_ops_fix_bitops

static void grow_and_negate(mp_int *a, int size, mp_int *b) {
    int i;
    /* Always add an extra digit so we can tell positive values
     * with a one in the highest bit apart from negative values
     * with a zero in the highest bit.
     */
    int actual_size = MAX(size, USED(a)) + 1;
    SIGN(b) = MP_ZPOS;
    mp_grow(b, actual_size);
    USED(b) = actual_size;
    for (i = 0; i < USED(a); i++) {
        DIGIT(b, i) = (~DIGIT(a, i)) & MP_MASK;
    }
    if (MP_NEG == SIGN(a)) {
        for (; i < actual_size; i++) {
            DIGIT(b, i) = MP_MASK;
        }
    }
    /* Note: this is never called with a containing only zeros because:
     * 1) we assume "negative zero" just does not happen (?)
     * 2) positive values only come here if they have a high bit of one
     * As such, this add cannot cause another grow.
     */
     mp_add_d(b, 1, b);
}

static void two_complement_bitop(mp_int *a, mp_int *b, mp_int *c,
        int (*mp_bitop)(mp_int *, mp_int *, mp_int *)) {

    mp_int d;
    mp_int e;
    mp_int *f;
    mp_int *g;

    f = a;
    g = b;
    if (MP_NEG == SIGN(a)) {
        mp_init(&d);
        grow_and_negate(a, USED(b), &d);
        f = &d;
    }
    if (MP_NEG == SIGN(b)) {
        mp_init(&e);
        grow_and_negate(b, USED(a), &e);
        g = &e;
    }
    mp_bitop(f, g, c);
    if (f == &d) mp_clear(&d);
    if (g == &e) mp_clear(&e);
    /* Use the fact that tomath clamps to detect signed results */
    if (USED(c) > MAX(USED(a),USED(b))) {
        mp_init(&d);
        grow_and_negate(c, c->used, &d);
        mp_clamp(&d);
        mp_copy(&d, c);
        mp_neg(c, c);
        mp_clear(&d);
    }
}