REORG: stconn: rename conn_stream.{c,h} to stconn.{c,h}

There's no more reason for keepin the code and definitions in conn_stream,
let's move all that to stconn. The alphabetical ordering of include files
was adjusted.
diff --git a/src/dns.c b/src/dns.c
index ee9b685..7c5c222 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -25,7 +25,6 @@
 #include <haproxy/channel.h>
 #include <haproxy/check.h>
 #include <haproxy/cli.h>
-#include <haproxy/conn_stream.h>
 #include <haproxy/dgram.h>
 #include <haproxy/dns.h>
 #include <haproxy/errors.h>
@@ -33,6 +32,7 @@
 #include <haproxy/log.h>
 #include <haproxy/ring.h>
 #include <haproxy/sc_strm.h>
+#include <haproxy/stconn.h>
 #include <haproxy/stream.h>
 #include <haproxy/tools.h>