MINOR: server: add a global list of all known servers

It's a real pain not to have access to the list of all registered servers,
because whenever there is a need to late adjust their configuration, only
those attached to regular proxies are seen, but not the peers, lua, logs
nor DNS.

What this patch does is that new_server() will automatically add the newly
created server to a global list, and it does so as well for the 1 or 2
statically allocated servers created for Lua. This way it will be possible
to iterate over all of them.
diff --git a/src/hlua.c b/src/hlua.c
index 52c4295..a093faf 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -48,7 +48,7 @@
 #include <haproxy/proxy-t.h>
 #include <haproxy/regex.h>
 #include <haproxy/sample.h>
-#include <haproxy/server-t.h>
+#include <haproxy/server.h>
 #include <haproxy/session.h>
 #include <haproxy/stats-t.h>
 #include <haproxy/stream.h>
@@ -9179,6 +9179,7 @@
 	socket_tcp.pendconns = EB_ROOT;
 	socket_tcp.idle_conns_tree = NULL;
 	socket_tcp.safe_conns_tree = NULL;
+	LIST_ADD(&servers_list, &socket_tcp.global_list);
 	socket_tcp.next_state = SRV_ST_RUNNING; /* early server setup */
 	socket_tcp.last_change = 0;
 	socket_tcp.conf.file = strdup("HLUA_INTERNAL");
@@ -9226,6 +9227,7 @@
 	socket_ssl.pendconns = EB_ROOT;
 	socket_ssl.idle_conns_tree = NULL;
 	socket_ssl.safe_conns_tree = NULL;
+	LIST_ADD(&servers_list, &socket_ssl.global_list);
 	socket_ssl.next_state = SRV_ST_RUNNING; /* early server setup */
 	socket_ssl.last_change = 0;
 	socket_ssl.conf.file = strdup("HLUA_INTERNAL");