go/doc: remove os.NewError anti-heuristic
go/doc: remove os.NewError anti-heuristic

It will be obsolete when error happens.

Submitting this now will make the error transition earlier,
at the cost of making a locally-built godoc viewing
/pkg/syscall or /pkg/os have some functions appear
under the Error type as constructors.

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/5305067

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