Unhide lines in rustdoc's doc -- Closes #11645
auto merge of #11810 : Armavica/rust/issue-11645, r=alexcrichton

The doc-generating tool comments out the lines that match `/$# /` (note the space), which is not what is wanted here. And it lets live the lines matching `/$#[^ ]/`. But we still want to see a space. So I replaced the normal space by a non breakable one, which fools the parser into displaying the line.