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/backend.c b/src/backend.c
index 4c2d9e8..d0d132b 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1599,17 +1599,17 @@
  * Please take care of keeping this list alphabetically sorted.
  */
 static struct acl_kw_list acl_kws = {{ },{
-	{ "avg_queue",     acl_parse_int,     smp_fetch_avg_queue_size, acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "be_conn",       acl_parse_int,     smp_fetch_be_conn,        acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "be_id",         acl_parse_int,     smp_fetch_be_id,          acl_match_int,     ACL_USE_NOTHING,      0           },
-	{ "be_sess_rate",  acl_parse_int,     smp_fetch_be_sess_rate,   acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "connslots",     acl_parse_int,     smp_fetch_connslots,      acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "nbsrv",         acl_parse_int,     smp_fetch_nbsrv,          acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "queue",         acl_parse_int,     smp_fetch_queue_size,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
-	{ "srv_conn",      acl_parse_int,     smp_fetch_srv_conn,       acl_match_int,     ACL_USE_NOTHING,      ARG1(1,SRV) },
-	{ "srv_id",        acl_parse_int,     smp_fetch_srv_id,         acl_match_int,     ACL_USE_RTR_INTERNAL, 0           },
-	{ "srv_is_up",     acl_parse_nothing, smp_fetch_srv_is_up,      acl_match_nothing, ACL_USE_NOTHING,      ARG1(1,SRV) },
-	{ "srv_sess_rate", acl_parse_int,     smp_fetch_srv_sess_rate,  acl_match_int,     ACL_USE_NOTHING,      ARG1(1,SRV) },
+	{ "avg_queue",     NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "be_conn",       NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "be_id",         NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      0           },
+	{ "be_sess_rate",  NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "connslots",     NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "nbsrv",         NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "queue",         NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,BE)  },
+	{ "srv_conn",      NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,SRV) },
+	{ "srv_id",        NULL, acl_parse_int,     acl_match_int,     ACL_USE_RTR_INTERNAL, 0           },
+	{ "srv_is_up",     NULL, acl_parse_nothing, acl_match_nothing, ACL_USE_NOTHING,      ARG1(1,SRV) },
+	{ "srv_sess_rate", NULL, acl_parse_int,     acl_match_int,     ACL_USE_NOTHING,      ARG1(1,SRV) },
 	{ /* END */ },
 }};