PRESUBMIT.py: accept variants on the copyright message that are present in the codebase.

Example files that this makes ok instead of flagging include:
  talk/base/signalthread_unittest.cc
  talk/base/thread_unittest.cc
  webrtc/base/signalthread_unittest.cc
  webrtc/base/thread.cc
  webrtc/base/thread.h
  webrtc/base/thread_unittest.cc

BUG=1027
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/19539006

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6235 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/talk/PRESUBMIT.py b/talk/PRESUBMIT.py
index aa46bb4..8e1a2e3 100644
--- a/talk/PRESUBMIT.py
+++ b/talk/PRESUBMIT.py
@@ -49,6 +49,7 @@
   current_year = int(input_api.time.strftime('%Y'))
   allowed_years = (str(s) for s in reversed(xrange(2004, current_year + 1)))
   years_re = '(' + '|'.join(allowed_years) + ')'
+  years_re = '%s(--%s)?' % (years_re, years_re)
   license_header = (
       r'.*? libjingle\n'
       r'.*? Copyright %(year)s,? Google Inc\.\n'