runtime: start new darwin/amd64 threads on correct stack,     then enable stack check.
runtime: start new darwin/amd64 threads on correct stack,
    then enable stack check.

R=r
http://codereview.appspot.com/165100

Triskite/willstone-goclone,Triskite/willstone-goclone,Triskite/willstone-goclone,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,bryanxu/go-zh,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,mhennings/marcohennings-go,scirelli/scirelli-go,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,npe9/noahevans-go9,d0f/go-zh,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,bryanxu/go-zh,mhennings/marcohennings-go,mhennings/marcohennings-go,scirelli/scirelli-go,bryanxu/go-zh,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,d0f/go-zh,npe9/noahevans-go9,npe9/noahevans-go9,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,bryanxu/go-zh,Triskite/willstone-goclone,webfd/go-zh,npe9/noahevans-go9,d0f/go-zh,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,scirelli/scirelli-go,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,mhennings/marcohennings-go,npe9/noahevans-go9,bryanxu/go-zh,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,scirelli/scirelli-go,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,npe9/noahevans-go9,npe9/noahevans-go9,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc