multiple definitions of ROUNDUP macro

[Luigi Rizzo]

The ROUNDUP macro, used to account for the space occupied by a sockaddr   
when passed through a routing socket, is defined in a zillion places:

src/usr.sbin/IPXrouted/startup.c:#define ROUNDUP(a) \
src/usr.sbin/arp/arp.c:#define ROUNDUP(a) \
src/usr.sbin/ndp/ndp.c:#define ROUNDUP(a) \
src/usr.sbin/ppp/defs.h:#define ROUNDUP(x) ((x) ? (1 + (((x) - 1) | (sizeof(longsrc/usr.sbin/route6d/route6d.c:#define ROUNDUP(a) \
src/usr.sbin/rwhod/rwhod.c:#define ROUNDUP(a) \
src/sys/net/route.c.orig:#define ROUNDUP(a) (a>0 ? (1 + (((a) - 1) | (sizeof(lonsrc/sys/net/rtsock.c:#define ROUNDUP(a) \

A similar macro, ADVANCE, has similar problems.
This is confusing at best, and a likely source of trouble.

If there are no objections I would like to replace it with a
centralised macro (possibly with a suitable name) which takes
a sockaddr * as argument and returns the rounded-up size of the
object as a result.

BTW, i notice that the rounding is to multiples of "sizeof(long)",
and i wonder if this is intentional, especially on 64-bit
architectures.

	cheers
	luigi