Clean up PRESUBMIT.py, and enable license check.

Fix the license header based on the example in:
http://src.chromium.org/viewvc/chrome/trunk/tools/depot_tools/presubmit_canned_checks.py?revision=107590&view=markup

BUG=None
TEST=Run presubmit checks on a dummy CL with Python and C code.

Review URL: https://webrtc-codereview.appspot.com/369002

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1511 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed