html/template: fix URL doc
html/template: fix URL doc

This is the easy part of issue 3528.
(What to do about "noescape" is the hard part, left open.)

Update issue 3528.

R=mikesamuel, r, dsymonds
CC=golang-dev
http://codereview.appspot.com/6493113

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