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

.travis.yml

@@ -5,7 +5,7 @@ dist: trusty
 sudo: required
 
 env:
-  - OPTS="--check-signed-off-travis --check-cppcheck --check-vera"
+  - OPTS="--check-signed-off-travis --check-cppcheck --check-vera --check-license"
   - OPTS="--jerry-tests --jerry-test-suite"
   - OPTS="--jerry-tests --jerry-test-suite --toolchain=cmake/toolchain_linux_armv7l.cmake" TIMEOUT=300 INSTALL_QEMU_ARM=yes
   - OPTS=--buildoption-test