[openib-general] Vendor specific MAD support

[Roland Dreier]

    Viswanath> Does openIB Gen2 stack umad/mad library support Vendor
    Viswanath> specific MAD extensions ?

The kernel's userspace MAD interface allows userspace to send and
receive arbitrary MADs containing any data at all that userspace wants.

I'm not sure what the existing libraries expose, but it's rather
trivial to code directly to the kernel interface if required.

 - R.