[MEDIUM] add support for RDP cookie persistence

The new statement "persist rdp-cookie" enables RDP cookie
persistence. The RDP cookie is then extracted from the RDP
protocol, and compared against available servers. If a server
matches the RDP cookie, then it gets the connection.
diff --git a/src/session.c b/src/session.c
index af6061f..d116ef2 100644
--- a/src/session.c
+++ b/src/session.c
@@ -850,6 +850,12 @@
 					if (!http_process_request_body(s, s->req, AN_REQ_HTTP_BODY))
 						break;
 				}
+
+				if (s->req->analysers & AN_REQ_PRST_RDP_COOKIE) {
+					last_ana |= AN_REQ_PRST_RDP_COOKIE;
+					if (!tcp_persist_rdp_cookie(s, s->req, AN_REQ_PRST_RDP_COOKIE))
+						break;
+				}
 			}
 		}