runtime: fix SI_USER for FreeBSD Ref: http://svnweb.freebsd.org/base/head/sys/sys/signal.h?revision=HEAD&view=markup
runtime: fix SI_USER for FreeBSD
Ref: http://svnweb.freebsd.org/base/head/sys/sys/signal.h?revision=HEAD&view=markup

R=golang-dev, devon.odell, r
CC=golang-dev
http://codereview.appspot.com/6490118

sanjosh/sanjos100-tipc,webfd/go-zh,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,rdp/rogerpack2005-golang,d0f/go-zh,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,scirelli/scirelli-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,d0f/go-zh,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,webfd/go-zh,webfd/go-zh,d0f/go-zh,d0f/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,webfd/go-zh,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,webfd/go-zh,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,webfd/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,bryanxu/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,d0f/go-zh,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,mhennings/marcohennings-go,bryanxu/go-zh,scirelli/scirelli-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof