cmd/godoc: when redirecting don't clear query string so that http://golang.org/pkg/runtime?m=all works.
cmd/godoc: when redirecting don't clear query string
so that http://golang.org/pkg/runtime?m=all works.

R=bradfitz
CC=golang-dev
https://codereview.appspot.com/7094046

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