REORG: include: move peers.h to haproxy/peers{,-t}.h

The cfg_peers external declaration was moved to the main file instead
of the type one. A few types were still missing from the proto, causing
warnings in the functions prototypes (proxy, stick_table).
diff --git a/src/stick_table.c b/src/stick_table.c
index aad4071..835b0a6 100644
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -21,6 +21,7 @@
 #include <haproxy/pool.h>
 #include <haproxy/list.h>
 #include <haproxy/net_helper.h>
+#include <haproxy/peers.h>
 #include <haproxy/task.h>
 #include <haproxy/tcp_rules.h>
 #include <haproxy/tools.h>
@@ -42,7 +43,6 @@
 #include <proto/stream.h>
 #include <proto/stream_interface.h>
 #include <proto/stick_table.h>
-#include <proto/peers.h>
 
 /* structure used to return a table key built from a sample */
 static THREAD_LOCAL struct stktable_key static_table_key;