Remedy compiler warnings on 32-bit builds related to integer width (invisible when building on 64-bit).
    a pointer to vmi_instance_t->size (which is a uint64_t) was passed to
    driver_get_memsize in core.c:

        driver_get_memsize(*vmi, &(*vmi)->size);

    the following results for 32-bit builds (where of course
    sizeof(long unsigned int) != sizeof(uint64_t), causing the warning):

        core.c: In function 'vmi_init_private':
        core.c:553:9: warning: passing argument 2 of 'driver_get_memsize' from
          incompatible pointer type [enabled by default]
        driver/interface.h:59:10: note: expected 'long unsigned int *' but argument
          is of type 'uint64_t *'
        core.c:597:9: warning: passing argument 2 of 'driver_get_memsize' from
          incompatible pointer type [enabled by default]
        driver/interface.h:59:10: note: expected 'long unsigned int *' but argument
          is of type 'uint64_t *'