Document how we use UDP sockets.

Comment changes only, no functional changes.

(cherry picked from commit d65986030a0f122623bae1ae197527438b7fbcd1)
Signed-off-by: Bruce A. Mah <bmah@es.net>

Conflicts:
	src/iperf_udp.c
Make UDP tests honor the -w option for setting the socket buffer
size.

This appears to be necessary on some long, high-bandwidth paths
to get sane results, either by reducing packet loss or by somehow
allowing the sending host of a test to go faster.

Fixes #219.

(cherry picked from commit 72ac83e7f27f5956f1822382a299c0e75a65c9aa)
Signed-off-by: Bruce A. Mah <bmah@es.net>

Conflicts:
	src/locale.c