title: how to add proxy support to boost::asio?
body: <p>In my desktop application I added access to various internet resources using boost::asio. All i do is sending http requests (i.e to map tile servers) and read the results.
  My code is based on the <a href="http://www.boost.org/doc/libs/1_48_0/doc/html/boost_asio/example/http/client/sync_client.cpp" rel="nofollow noreferrer">asio sync_client sample</a>.</p>
  
  <p>Now i get reports from customers who are unable to use these functions as they are running a proxy in their company. In a web browser they can enter the address of their proxy and everything is fine. Our application is unable to download data.</p>
  
  <p>How can i add such support to my application?</p>