Avoid shifts of negative values inflateMark().

The C standard says that bit shifts of negative integers is
undefined.  This casts to unsigned values to assure a known
result.
int ZEXPORT inflateSync(strm)
z_streamp strm;
{
    unsigned len;               /* number of bytes to look at or looked at */
    unsigned long in, out;      /* temporary to save total_in and total_out */
    unsigned char buf[4];       /* to restore bit buffer to byte string */
    struct inflate_state FAR *state;

    /* check parameters */
    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
    state = (struct inflate_state FAR *)strm->state;
    if (strm->avail_in == 0 && state->bits < 8) return Z_BUF_ERROR;

    /* if first time, start search in bit buffer */
    if (state->mode != SYNC) {
        state->mode = SYNC;
        state->hold <<= state->bits & 7;
        state->bits -= state->bits & 7;
        len = 0;
        while (state->bits >= 8) {
            buf[len++] = (unsigned char)(state->hold);
            state->hold >>= 8;
            state->bits -= 8;
        }
        state->have = 0;
        syncsearch(&(state->have), buf, len);
    }

    /* search available input */
    len = syncsearch(&(state->have), strm->next_in, strm->avail_in);
    strm->avail_in -= len;
    strm->next_in += len;
    strm->total_in += len;

    /* return no joy or set up to restart inflate() on a new block */
    if (state->have != 4) return Z_DATA_ERROR;
    in = strm->total_in;  out = strm->total_out;
    inflateReset(strm);
    strm->total_in = in;  strm->total_out = out;
    state->mode = TYPE;
    return Z_OK;
}

int ZEXPORT inflateSync(strm)
z_streamp strm;
{
    unsigned len;               /* number of bytes to look at or looked at */
    unsigned long in, out;      /* temporary to save total_in and total_out */
    unsigned char buf[4];       /* to restore bit buffer to byte string */
    struct inflate_state FAR *state;

    /* check parameters */
    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
    state = (struct inflate_state FAR *)strm->state;
    if (strm->avail_in == 0 && state->bits < 8) return Z_BUF_ERROR;

    /* if first time, start search in bit buffer */
    if (state->mode != SYNC) {
        state->mode = SYNC;
        state->hold <<= state->bits & 7;
        state->bits -= state->bits & 7;
        len = 0;
        while (state->bits >= 8) {
            buf[len++] = (unsigned char)(state->hold);
            state->hold >>= 8;
            state->bits -= 8;
        }
        state->have = 0;
        syncsearch(&(state->have), buf, len);
    }

    /* search available input */
    len = syncsearch(&(state->have), strm->next_in, strm->avail_in);
    strm->avail_in -= len;
    strm->next_in += len;
    strm->total_in += len;

    /* return no joy or set up to restart inflate() on a new block */
    if (state->have != 4) return Z_DATA_ERROR;
    in = strm->total_in;  out = strm->total_out;
    inflateReset(strm);
    strm->total_in = in;  strm->total_out = out;
    state->mode = TYPE;
    return Z_OK;
}
