Make djbdns to ignore SIGPIPE

TCP queries have the potential to cause dnscache to catch a SIGPIPE if the
remote side closes the socket before the write finishes. This causes dnscache
to exit. There is a trivial patch which causes djbdns to ignore
SIGPIPE.

http://tinydns.org/marc.theaimsgroup.com/index.html%3fl=djbdns&m=104812086607532&w=2

Signed-off-by: Giam Teck Choon <giamteckchoon@gmail.com>