Make the pushers lang field column longer

To accommodate things like zh-Hans-CN

Fixes https://github.com/vector-im/riot-ios/issues/1031

synapse/storage/schema/delta/40/pushers.sql

+/* Copyright 2017 Vector Creations Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+CREATE TABLE IF NOT EXISTS pushers2 (
+    id BIGINT PRIMARY KEY,
+    user_name TEXT NOT NULL,
+    access_token BIGINT DEFAULT NULL,
+    profile_tag VARCHAR(32) NOT NULL,
+    kind VARCHAR(8) NOT NULL,
+    app_id VARCHAR(64) NOT NULL,
+    app_display_name VARCHAR(64) NOT NULL,
+    device_display_name VARCHAR(128) NOT NULL,
+    pushkey TEXT NOT NULL,
+    ts BIGINT NOT NULL,
+    lang VARCHAR(16),
+    data TEXT,
+    last_stream_ordering INTEGER,
+    last_success BIGINT,
+    failing_since BIGINT,
+    UNIQUE (app_id, pushkey, user_name)
+);
+
+INSERT INTO pushers2 SELECT * FROM PUSHERS;
+
+DROP TABLE PUSHERS;
+
+ALTER TABLE pushers2 RENAME TO pushers;