buf fix: make FD.Read, FD.Write work for empty buffers
buf fix: make FD.Read, FD.Write work for empty buffers

R=r
DELTA=8  (6 added, 0 deleted, 2 changed)
OCL=19273
CL=19275

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