MAJOR: acl: convert all ACL requires to SMP use+val instead of ->requires

The ACLs now use the fetch's ->use and ->val to decide upon compatibility
between the place where they are used and where the information are fetched.
The code is capable of reporting warnings about very fine incompatibilities
between certain fetches and an exact usage location, so it is expected that
some new warnings will be emitted on some existing configurations.

Two degrees of detection are provided :
  - detecting ACLs that never match
  - detecting keywords that are ignored

All tests show that this seems to work well, though bugs are still possible.
diff --git a/include/proto/acl.h b/include/proto/acl.h
index 1471dae..39cbf46 100644
--- a/include/proto/acl.h
+++ b/include/proto/acl.h
@@ -97,10 +97,20 @@
  */
 int acl_exec_cond(struct acl_cond *cond, struct proxy *px, struct session *l4, void *l7, unsigned int opt);
 
-/* Reports a pointer to the first ACL used in condition <cond> which requires
- * at least one of the USE_FLAGS in <require>. Returns NULL if none matches.
+/* Returns a pointer to the first ACL conflicting with usage at place <where>
+ * which is one of the SMP_VAL_* bits indicating a check place, or NULL if
+ * no conflict is found. Only full conflicts are detected (ACL is not usable).
+ * Use the next function to check for useless keywords.
+ */
+const struct acl *acl_cond_conflicts(const struct acl_cond *cond, unsigned int where);
+
+/* Returns a pointer to the first ACL and its first keyword to conflict with
+ * usage at place <where> which is one of the SMP_VAL_* bits indicating a check
+ * place. Returns true if a conflict is found, with <acl> and <kw> set (if non
+ * null), or false if not conflict is found. The first useless keyword is
+ * returned.
  */
-struct acl *cond_find_require(const struct acl_cond *cond, unsigned int require);
+int acl_cond_kw_conflicts(const struct acl_cond *cond, unsigned int where, struct acl const **acl, struct acl_keyword const **kw);
 
 /*
  * Find targets for userlist and groups in acl. Function returns the number