[RFC][PATCH] net drivers and cache alignment

One of the [many] nice properties of the traditional Don Becker drivers 
has been that often the driver-private structures are arranged such that 
  the structure is broken up on cacheline boundaries.  The RX thread has 
a cacheline, the TX thread has a cacheline, etc.  Jes Sorensen also 
independently, in his review of 8139cp.c, suggested that the 
driver-private struct be update with attention to cacheline boundaries.

Early next year, I would like to start cleaning up some of the net 
drivers along these lines (no pun intended).  To make it easier for 
vendors and random coders to cacheline-align struct members, I would 
like to make more explicit these cacheline boundaries, in a manner that 
is portable between 32-bit and 64-bit systems.

I attach a sample implementation, and request feedback on this approach. 
   The general idea is to make implementing this sort of concept "harder 
to screw up."