syscall: StartProcess Chroot and Credential.
syscall: StartProcess Chroot and Credential.

R=rsc, iant, agl1
CC=golang-dev
http://codereview.appspot.com/4280065

Committer: Adam Langley <db68fba232b2c49ed3e9d3081df349dde7b61dfd@golang.org>

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