Common: introduce new io code To avoid code duplication in accept, connect, reading and writing we add a new set of classes in `io` namespaces located in the following files: - stream.hpp, acceptor.hpp, connector.hpp These classes consist of pure abstract interfaces for I/O. Then we reimplement them in the following files: - socket_stream.hpp, socket_acceptor.hpp, socket_connector.hpp, - tls_stream.hpp, tls_acceptor.hpp, tls_conncetor.hpp (for SSL). This allows future independant connections such as DBus, fifo or any other fancy optional stuff. We also no longer need large class hierarchy such as `connection` for irccdctl controller or transport_server, transport_client classes.

--- a/irccdctl/watch_cli.cpp	Fri Apr 06 22:06:07 2018 +0200
+++ b/irccdctl/watch_cli.cpp	Tue Apr 10 21:20:30 2018 +0200
@@ -177,9 +177,9 @@
 
 void get_event(ctl::controller& ctl, std::string fmt)
 {
-    ctl.recv([&ctl, fmt] (auto code, auto message) {
+    ctl.read([&ctl, fmt] (auto code, auto message) {
         if (code)
-            throw boost::system::system_error(code);
+            throw std::system_error(code);
 
         const auto event = json_util::parser(message).get<std::string>("event");
         const auto it = events.find(event ? *event : "");