Merge pull request cpp-netlib#402 from leecoder/0.11-devel

Fixes cpp-netlib#358 - avoid self join

Author: deanberris

boost/network/protocol/http/client/async_impl.hpp

@@ -64,7 +64,9 @@ struct async_client
   ~async_client() throw() {
     sentinel_.reset();
     if (lifetime_thread_.get()) {
-      lifetime_thread_->join();
+      if (lifetime_thread_->get_id() != boost::this_thread::get_id()) {
+        lifetime_thread_->join();
+      }
       lifetime_thread_.reset();
     }
   }