MAJOR: acl: make all ACLs reference the fetch function via a sample.

ACL fetch functions used to directly reference a fetch function. Now
that all ACL fetches have their sample fetches equivalent, we can make
ACLs reference a sample fetch keyword instead.

In order to simplify the code, a sample keyword name may be NULL if it
is the same as the ACL's, which is the most common case.

A minor change appeared, http_auth always expects one argument though
the ACL allowed it to be missing and reported as such afterwards, so
fix the ACL to match this. This is not really a bug.
diff --git a/src/listener.c b/src/listener.c
index e9ce07e..28c5bf0 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -653,8 +653,8 @@
  * Please take care of keeping this list alphabetically sorted.
  */
 static struct acl_kw_list acl_kws = {{ },{
-	{ "dst_conn",   acl_parse_int,   smp_fetch_dconn,    acl_match_int, ACL_USE_NOTHING, 0 },
-	{ "so_id",      acl_parse_int,   smp_fetch_so_id,    acl_match_int, ACL_USE_NOTHING, 0 },
+	{ "dst_conn",  NULL, acl_parse_int, acl_match_int, ACL_USE_NOTHING, 0 },
+	{ "so_id",     NULL, acl_parse_int, acl_match_int, ACL_USE_NOTHING, 0 },
 	{ /* END */ },
 }};