This is still somewhat experimental. Tested between 2 similar boxes
so far. There is much potential for performance improvement. For now,
I've changed the gmac code to accept any data alignment, as the "char *"
pointer suggests. As the code is practically used, 32-bit alignment
can be assumed, at the cost of data copies. I don't know whether
bytewise access or copies are worse performance-wise. For efficient
implementations using SSE2 instructions on x86, even stricter
alignment requirements might arise.
