duckduckgo no longer sends any referrer for http search results
I searched for "test" clicked on wikipedia and my referrer was: http://duckduckgo.com/post.html
I get http://duckduckgo.com/post.html with Firefox.
No referrer with Safari or Chrome.
Hmm... DDG doesn't rank Piwik highly in its search results for "web analytics"...
Current beaviour is OK: will show http://duckduckgo.com/post.html as external website.
I propose to leave it in the search engines list in case there are still referrers passing keywords.
(In ) Fixes #2813