MINOR: http: generic pointer to rule argument

Add a void *data which can be used as a generic storage for rule
arguments.
diff --git a/include/types/proto_http.h b/include/types/proto_http.h
index 50e6a92..e1d04d6 100644
--- a/include/types/proto_http.h
+++ b/include/types/proto_http.h
@@ -431,6 +431,7 @@
 		int loglevel;                  /* log-level value for HTTP_REQ_ACT_SET_LOGL */
 		int tos;                       /* tos value for HTTP_REQ_ACT_SET_TOS */
 		int mark;                      /* nfmark value for HTTP_REQ_ACT_SET_MARK */
+		void *data;                    /* generic pointer for module or external rule */
 		struct {
 			char *ref;             /* MAP or ACL file name to update */
 			struct list key;       /* pattern to retrieve MAP or ACL key */
@@ -454,6 +455,7 @@
 		int loglevel;                  /* log-level value for HTTP_RES_ACT_SET_LOGL */
 		int tos;                       /* tos value for HTTP_RES_ACT_SET_TOS */
 		int mark;                      /* nfmark value for HTTP_RES_ACT_SET_MARK */
+		void *data;                    /* generic pointer for module or external rule */
 		struct {
 			char *ref;             /* MAP or ACL file name to update */
 			struct list key;       /* pattern to retrieve MAP or ACL key */