std C/C++ patch #9

[Eddie Kohler]

Hi Scott,

Patches #6 and #9 are now in. As far as I know, this leaves only
__attribute__((packed)).

It seems to me like we need to figure out two things for
__attribute__((packed)):

1. What to do about sizeof(click_ether)?

   It would be OK, but very annoying, to deprecate sizeof(click_ether), I
   suppose -- and, similarly, sizoef(click_ip), etc. -- and move to some
   macro convention. :P

2. What about structures that actually need to be packed (i.e., they
   contain unaligned uint32_ts et al.)?

   I don't want to fix this one without help from the compiler. One could
   write lovely macros for accessing unaligned integers, but, in a word,
   barf.

I think what I'd like to do here is wait to see if the relevant compilers
support what we need. Does KCC/Sun CC have a #pragma that would let
sizeof(click_ether) == 14, and allow unaligned accesses within a particular
kind of structure? If so, we'll need to decide on a set of macros that
work on any compiler.

Eddie