codereview: add release branch support
codereview: add release branch support

Note that if you are working on the upcoming release
branch you have to point your extension path to a
copy of lib/codereview/codereview.py that won't change
as the repository flips between release-branch and default branch.
This warning should only apply to this one branch and only to rsc,
but you never know.

R=adg
CC=golang-dev
http://codereview.appspot.com/4446076

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