CLEANUP: proxy: rename "block_cond" to "block_rules"

Next patch will make them real rules, not only conditions. This separate
patch makes the next one more readable.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 4c0c660..cf277fd 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -228,7 +228,7 @@
 	struct list acl;                        /* ACL declared on this proxy */
 	struct list http_req_rules;		/* HTTP request rules: allow/deny/... */
 	struct list http_res_rules;		/* HTTP response rules: allow/deny/... */
-	struct list block_cond;                 /* early blocking conditions (chained) */
+	struct list block_rules;                /* http-request block rules to be inserted before other ones */
 	struct list redirect_rules;             /* content redirecting rules (chained) */
 	struct list switching_rules;            /* content switching rules (chained) */
 	struct list persist_rules;		/* 'force-persist' and 'ignore-persist' rules (chained) */