Makefile: remove 'install' target. fixes #1717

Signed-off-by: Daira Hopwood <david-sarah@jacaranda.org>
iputil.py: retry address queries on EINTR. fixes #1381

Signed-off-by: Daira Hopwood <david-sarah@jacaranda.org>
iputil.py: refactor address-finding code to treat all Unices the same.
refs #1988, #982, #1064, #1536, #1935
fixes #898, #1707, #1918

Signed-off-by: Daira Hopwood <david-sarah@jacaranda.org>
iputil.py: minor cleanup to avoid dropping a Deferred.

Signed-off-by: Daira Hopwood <david-sarah@jacaranda.org>