cmd/godoc: initialize filesystem and metadata for -url
cmd/godoc: initialize filesystem and metadata for -url

Unlike when using -http, godoc -url didn't initialize the "filesystem"
and metadata that are used when generating responses. This CL adds this
initialization, so that -url provides the same results as an HTTP
request when using -http.

Fixes issue 4335.

R=golang-dev, minux.ma
CC=golang-dev
http://codereview.appspot.com/6817075

Committer: Shenghou Ma <b563c57947dc20eb81988e3e3c22786764c14ca8@gmail.com>

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