Forbid access to _local_docs for non-system dbs

COUCHDB-1145
diff --git a/src/couch_mrview_http.erl b/src/couch_mrview_http.erl
index 75e2c54..dc50f59 100644
--- a/src/couch_mrview_http.erl
+++ b/src/couch_mrview_http.erl
@@ -180,7 +180,7 @@
     all_docs_req(Req, Db, Keys, undefined).
 
 all_docs_req(Req, Db, Keys, NS) ->
-    case couch_db:is_system_db(Db) of
+    case is_restricted(Db, NS) of
     true ->
         case (catch couch_db:check_is_admin(Db)) of
         ok ->
@@ -200,6 +200,11 @@
         do_all_docs_req(Req, Db, Keys, NS)
     end.
 
+is_restricted(_Db, <<"_local">>) ->
+    true;
+is_restricted(Db, _) ->
+    couch_db:is_system_db(Db).
+
 is_public_fields_configured(Db) ->
     DbName = ?b2l(Db#db.name),
     case config:get("couch_httpd_auth",