os: make RemoveAll() work on windows
os: make RemoveAll() work on windows

R=golang-dev, rsc1
CC=golang-dev
http://codereview.appspot.com/2212041

Committer: Alex Brainman <54ba58c8441b5eff861de6b4e5ee46baf086b142@gmail.com>

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