[MINOR] acl: add support for matching of RDP cookies

The RDP protocol is quite simple and documented, which permits
an easy detection and extraction of cookies. It can be useful
to match the MSTS cookie which can contain the username specified
by the client.
diff --git a/include/proto/proto_tcp.h b/include/proto/proto_tcp.h
index 61ec0bd..c188c27 100644
--- a/include/proto/proto_tcp.h
+++ b/include/proto/proto_tcp.h
@@ -33,6 +33,8 @@
 void tcpv6_add_listener(struct listener *listener);
 int tcp_bind_listener(struct listener *listener, char *errmsg, int errlen);
 int tcp_inspect_request(struct session *s, struct buffer *req, int an_bit);
+int acl_fetch_rdp_cookie(struct proxy *px, struct session *l4, void *l7, int dir,
+                         struct acl_expr *expr, struct acl_test *test);
 
 #endif /* _PROTO_PROTO_TCP_H */