[openib-general] user-mode data strucures

[Roland Dreier]

    Tom> I think that just moves the alignment issue to the first word
    Tom> of the sge since it's first element is a uint64_t. I think
    Tom> the only thing that works across the board without packing is
    Tom> to #if __BITS_IN_WORD==32 add a pad word after
    Tom> *next. erf...ugly code.

Actually I think we're OK -- the sg_list member is a pointer, which will
be 32 bits too.  It looks to me like ibv_send_wr has an even number of
32-bit quantities before the union, so everything should pack naturally.