net: fix setsockopt for openbsd
net: fix setsockopt for openbsd

s/TCP_KEEPALIVE/SO_KEEPALIVE/ to unbreak build on OpenBSD.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/11345044

Committer: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

d0f/go-zh,mhennings/marcohennings-go,webfd/go-zh,webfd/go-zh,webfd/go-zh,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,bryanxu/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,d0f/go-zh,mhennings/marcohennings-go,mhennings/marcohennings-go,d0f/go-zh,bryanxu/go-zh,d0f/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,bryanxu/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,d0f/go-zh,webfd/go-zh,webfd/go-zh