Add license checking (#1353)

It's stated in the Guidelines that all contributions must be under
the Apache License 2.0. To avoid potential mistakes from manual
reviews, this patch adds the check-license.py script to
automatically check all source files for license headers.

Travis CI is also configured to run the check.

Fallout: it turned out that some files already in the code base
either miss a license header or have some minor typo differences.
The patch fixes up some of these deficiences.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

tools/unit-tests/gen-test-libm.c

@@ -33,7 +33,23 @@
 int
 main (int argc, char **args)
 {
-  printf ("/*\n"
+  printf ("/* Copyright 2016 Samsung Electronics Co., Ltd.\n"
+          " * Copyright 2016 University of Szeged.\n"
+          " *\n"
+          " * Licensed under the Apache License, Version 2.0 (the \"License\");\n"
+          " * you may not use this file except in compliance with the License.\n"
+          " * You may obtain a copy of the License at\n"
+          " *\n"
+          " *     http://www.apache.org/licenses/LICENSE-2.0\n"
+          " *\n"
+          " * Unless required by applicable law or agreed to in writing, software\n"
+          " * distributed under the License is distributed on an \"AS IS\" BASIS\n"
+          " * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
+          " * See the License for the specific language governing permissions and\n"
+          " * limitations under the License.\n"
+          " */\n"
+          "\n"
+          "/*\n"
           " * Generated by tools/gen-test-libm.sh\n"
           " * DO NOT EDIT!!!\n"
           " */\n");