Size mismatch when serializing error objects

[maximk]

The following code:

    obj_p x = error(5, "myerror");
    obj_p fmt = obj_fmt(x, B8_TRUE);
    printf("%.*s", (uint32_t)fmt->len, as_string(fmt));
    drop_obj(fmt);

    int size = size_obj(x);

    u8_t buf[4096];
    int size1 = save_obj(buf, size, x);

    printf("size  = %d\n", size);
    printf("size1 = %d\n", size1);

produces this output:

•• [E005] error: type mismatch myerror
size  = 10
size1 = 15

Also, load_obj() moves the pointer not according to the size in the header.