Timeout if UDP port isn't reachable

Add timeout to the UDP socket. Without it client would block infinitely
if creating a control connection succeeds, but UDP packets are dropped
by firewall.
Add ifdef to the SO_RCVTIMEO code

Not all platforms have a SO_RCVTIMEO socket option.
Update documentation site for 3.0.10.
Ignore set_test_zerocopy if host does not support it
Merge pull request #233 from candlerb/candlerb-zerocopy-force

Ignore set_test_zerocopy if host does not support it
Add one-off mode, where the server serves exactly one request.

Primarily useful for bwctl integration, this is enabled with the -1
and/or --one-off flags.

Fixes #230, based on a patch by @i2aaron.

Signed-off-by: Bruce A. Mah <bmah@es.net>
Merge pull request #222 from hasso/timeout-udp

Timeout if UDP port isn't reachable.

This handles the case that a control connection succeeds but UDP packets are blocked by a firewall.