MEDIUM: http: add support for "http-request tarpit" rule

The "reqtarpit" rule is not very handy to use. Now that we have more
flexibility with "http-request", let's finally make the tarpit rules
usable there.

There are still semantical differences between apply_filters_to_request()
and http_req_get_intercept_rule() because the former updates the counters
while the latter does not. So we currently have almost similar code leafs
for similar conditions, but this should be cleaned up later.
diff --git a/include/types/proto_http.h b/include/types/proto_http.h
index ef81a12..12e446f 100644
--- a/include/types/proto_http.h
+++ b/include/types/proto_http.h
@@ -240,6 +240,7 @@
 	HTTP_REQ_ACT_UNKNOWN = 0,
 	HTTP_REQ_ACT_ALLOW,
 	HTTP_REQ_ACT_DENY,
+	HTTP_REQ_ACT_TARPIT,
 	HTTP_REQ_ACT_AUTH,
 	HTTP_REQ_ACT_ADD_HDR,
 	HTTP_REQ_ACT_SET_HDR,