CI check generate code (#4998)

* call reflection code generation from tests

This simplifies instructions to contributors so they don't forget to update
reflection code.

* add error handling to generate_code scripts

Let them propagate their errors instead of swallowing them so they show
up when called in CI.

* apply editorconfig to shell scripts

* use ordered map in dart codegen

Using an unordered map in the codegen can lead to spurious diffs in the
generated dart code.

* add CI check for generate_code being run

* update reflection_generated.h

* disable diff-check for monster_test.bfbs

Work around #5008.

.travis/check-generate-code.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+#
+# Copyright 2018 Google Inc. All rights reserved.
+#
+# 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.
+set -e
+
+cd tests
+./generate_code.sh
+cd ..
+
+# TODO: Linux and macos builds produce differences here for some reason.
+git checkout HEAD -- tests/monster_test.bfbs
+
+if ! git diff --quiet; then
+  echo >&2
+  echo "ERROR: ********************************************************" >&2
+  echo "ERROR: The following differences were found after running the" >&2
+  echo "ERROR: tests/generate_code.sh script.  Maybe you forgot to run" >&2
+  echo "ERROR: it after making changes in a generator or schema?" >&2
+  echo "ERROR: ********************************************************" >&2
+  echo >&2
+  git diff --binary --exit-code
+fi