cleanup: Changes for c++17

This cleanup adjusts the rTorrent code to comply with c++17 standard. It also simplifies various parts of the code.

src/core/http_queue.cc

@@ -47,7 +47,7 @@ namespace core {
 
 HttpQueue::iterator
 HttpQueue::insert(const std::string& url, std::iostream* s) {
-  std::auto_ptr<CurlGet> h(m_slot_factory());
+  std::unique_ptr<CurlGet> h(m_slot_factory());
   
   h->set_url(url);
   h->set_stream(s);