Code in header results into HTML in the roff output

[paravoid]

The manpage:

## this is `code`

results into this output:

.SH "this is <code>code</code>"

[apjanke]

Yep, that's ugly. Let's fix that.

Will probably need to modify this:

        when 'h2'
          macro 'SH', quote(escape(node.inner_html))
        when 'h3'
          macro 'SS', quote(escape(node.inner_html))

to do a special inline_filter on the contents to remove or process markup instead of just escaping it.

Scheduling for version 0.11.