Hotfix for very long http headers
Fix stupid mistake, don't know why gcc didn't complained locally
jsoninfo: HTTP headers with CORS (if requested)

The new "httpheaders" parameter prepends HTTP headers to the reply.
Cross-origin resource sharing headers (CORS) are included in reply
allowing the json retrieval by javascript applications not served
by olsrd itself.
This will allow to easily develop js applications running directly
into the browser.