[MINOR] add the fiprm and beprm indirections to struct proxy

A proxy will be able to borrow parameters from another one.
In particular, the filters will be inheritable from another
proxy, and the backend parameters too.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 9592247..b3747c4 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1964,6 +1964,8 @@
 	}
 
 	while (curproxy != NULL) {
+		curproxy->fiprm = curproxy->beprm = curproxy;
+
 		if (curproxy->state == PR_STSTOPPED) {
 			curproxy = curproxy->next;
 			continue;