Move all the connect() logic from TCPSocketHandler into a subclass

This way, TCPSocketHandler only deal with the message sending/receiving, not
the connect() or anything else.  This will be used for implementing servers
(because when a client is accepted, we don’t need all the connect() and dns
resolution stuff).

louloulibs/xmpp/xmpp_component.cpp

@@ -39,7 +39,7 @@ static std::set<std::string> kickable_errors{
     };
 
 XmppComponent::XmppComponent(std::shared_ptr<Poller> poller, const std::string& hostname, const std::string& secret):
-  TCPSocketHandler(poller),
+  TCPClientSocketHandler(poller),
   ever_auth(false),
   first_connection_try(true),
   secret(secret),

louloulibs/xmpp/xmpp_component.hpp

@@ -2,7 +2,7 @@
 
 
 #include <xmpp/adhoc_commands_handler.hpp>
-#include <network/tcp_socket_handler.hpp>
+#include <network/tcp_client_socket_handler.hpp>
 #include <xmpp/xmpp_parser.hpp>
 #include <xmpp/body.hpp>
 
@@ -40,7 +40,7 @@
  *
  * TODO: implement XEP-0225: Component Connections
  */
-class XmppComponent: public TCPSocketHandler
+class XmppComponent: public TCPClientSocketHandler
 {
 public:
   explicit XmppComponent(std::shared_ptr<Poller> poller, const std::string& hostname, const std::string& secret);