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/tests/src/libirccd/command-server-kick/main.cpp	Fri Apr 06 22:06:07 2018 +0200
+++ b/tests/src/libirccd/command-server-kick/main.cpp	Tue Apr 10 21:20:30 2018 +0200
@@ -45,7 +45,7 @@
 
 BOOST_AUTO_TEST_CASE(basic)
 {
-    ctl_->send({
+    ctl_->write({
         { "command",    "server-kick"       },
         { "server",     "test"              },
         { "target",     "francis"           },
@@ -67,7 +67,7 @@
 
 BOOST_AUTO_TEST_CASE(noreason)
 {
-    ctl_->send({
+    ctl_->write({
         { "command",    "server-kick"       },
         { "server",     "test"              },
         { "target",     "francis"           },