TODO for udpsend

Allow specification of a UDP payload.
There is some code presently commented-out for doing this, but it's a mess.

Allow specification of IP options.

Allow specification of IP TOS.

Port to other platforms; stop ignoring most of what autoconf learns.
(Although the udpsend build process is autoconf-based, at
this time udpsend ignores almost everything autoconf discovers
about your system.  The product was developed on Solaris 7 with gcc 2.95.2,
and has not been ported to other platforms.  Despite the use of autoconf, the
code merrily makes assumptions that are only valid on Solaris 7.)
The use of autoconf here is mostly to provide a framework in case the
product is ported to other platforms in the future.