MINOR: http-rules: Use http_reply structure for http return rules

No real change here. Instead of using an internal structure to the action rule,
the http return rules are now stored as an http reply. The main change is about
the action type. It is now always set to ACT_CUSTOM. The http reply type is used
to know how to evaluate the rule.
diff --git a/include/types/action.h b/include/types/action.h
index 1a5a594..8d68f6d 100644
--- a/include/types/action.h
+++ b/include/types/action.h
@@ -26,6 +26,7 @@
 
 #include <types/applet.h>
 #include <types/stick_table.h>
+#include <types/http_htx.h>
 
 enum act_from {
 	ACT_F_TCP_REQ_CON, /* tcp-request connection */
@@ -128,16 +129,7 @@
 			int status;            /* status code */
 			struct buffer *errmsg; /* HTTP error message, may be NULL */
 		} http_deny;                   /* args used by HTTP deny rules */
-		struct {
-			int status;
-			char *ctype;
-			struct list *hdrs;
-			union {
-				struct list   fmt;
-				struct buffer obj;
-				struct buffer *errmsg;
-			} body;
-		} http_return;
+		struct http_reply *http_reply; /* HTTP response to be used by return rules */
 		struct redirect_rule *redir;   /* redirect rule or "http-request redirect" */
 		struct {
 			char *ref;             /* MAP or ACL file name to update */