[lwip-members] include files for structure packing

[Florian Schulze]

I already brought this up in the normal mailinglist, but got no definite
answer yet.

On Windows I can't define a macro to do the packing, because no # is
allowed in macros, this rules out #pragmas for packing and #includes. So
I would add two include files begin_pack_struct.h and end_pack_struct.h
which then would be included before and after the relevant structs. Those
include files would be placed in the arch directorys for every
architecture. Would this be ok and in which directory they should be then?

Florian