MAJOR: acl: make use of the new sample struct and get rid of acl_test

This change is invasive in lines of code but not much in terms of
functionalities as it's mainly a replacement of struct acl_test
with struct sample.
diff --git a/src/auth.c b/src/auth.c
index b650a45..f737fce 100644
--- a/src/auth.c
+++ b/src/auth.c
@@ -167,12 +167,12 @@
 }
 
 int
-acl_match_auth(struct acl_test *test, struct acl_pattern *pattern)
+acl_match_auth(struct sample *smp, struct acl_pattern *pattern)
 {
 
-	struct userlist *ul = test->ctx.a[0];
-	char *user = test->ctx.a[1];
-	char *pass = test->ctx.a[2];
+	struct userlist *ul = smp->ctx.a[0];
+	char *user = smp->ctx.a[1];
+	char *pass = smp->ctx.a[2];
 	unsigned int group_mask = pattern->val.group_mask;
 
 	if (check_user(ul, group_mask, user, pass))