net: fix crashing Read/Write when passed empty slice on windows
net: fix crashing Read/Write when passed empty slice on windows

Fixes issue 921.

R=rsc
CC=golang-dev
http://codereview.appspot.com/1862043

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

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