Utility for checking the encoding and line ending of source files (#5188)

* Add utility for checking the encoding of source files

- accept source files with ASCII or UTF-8 without BOM
- accept only CRLF line ending

* Fix non-ascii symbol in idl_parcer.cpp

* Remove BOM from test.cpp

.travis/check-sources.sh

@@ -0,0 +1,33 @@
+#!/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
+
+if [ -n "$1" ]; then
+  scan_dir="$1"
+else
+  scan_dir="$( pwd )"
+fi
+
+py_checker="$0.py"
+
+echo "scan root directory = '$scan_dir'"
+python3 --version
+# Scan recursively and search all *.cpp and *.h files using regex patterns.
+# Assume that script running from a root of Flatbuffers working dir.
+python3 $py_checker "ascii" "$scan_dir/include" "\.h$"
+python3 $py_checker "ascii" "$scan_dir/src"     "\.cpp$"
+python3 $py_checker "ascii" "$scan_dir/tests"   "\.h$"
+python3 $py_checker "utf-8" "$scan_dir/tests"   "\.cpp$"