spec: Allow omission of low slice bound
spec: Allow omission of low slice bound

See also http://codereview.appspot.com/1957045/

R=gri, rsc, r
CC=golang-dev
http://codereview.appspot.com/2163042

Committer: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

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