MINOR: pattern: separe list element from the data part.

This commit separes the "struct list" used for the chain the "struct
pattern" which contain the pattern data. Later, this change will permit
to manipulate lists ans trees with the same "struct pattern".
diff --git a/src/acl.c b/src/acl.c
index 2a3756c..26c58e7 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -133,7 +133,7 @@
 	__label__ out_return, out_free_expr, out_free_pattern;
 	struct acl_expr *expr;
 	struct acl_keyword *aclkw;
-	struct pattern *pattern;
+	struct pattern_list *pattern;
 	int patflags;
 	const char *arg;
 	struct sample_expr *smp = NULL;
@@ -1160,7 +1160,7 @@
 
 	struct acl *acl;
 	struct acl_expr *expr;
-	struct pattern *pattern;
+	struct pattern_list *pattern;
 	int cfgerr = 0;
 
 	list_for_each_entry(acl, &p->acl, list) {
@@ -1185,9 +1185,9 @@
 
 				/* For each pattern, check if the group exists. */
 				list_for_each_entry(pattern, &expr->pat.patterns, list) {
-					if (!check_group(expr->smp->arg_p->data.usr, pattern->ptr.str)) {
+					if (!check_group(expr->smp->arg_p->data.usr, pattern->pat.ptr.str)) {
 						Alert("proxy %s: acl %s %s(): invalid group '%s'.\n",
-						      p->id, acl->name, expr->kw, pattern->ptr.str);
+						      p->id, acl->name, expr->kw, pattern->pat.ptr.str);
 						cfgerr++;
 					}
 				}