**/*.py: use /usr/bin/env to find python

src/trusted/validator_x86/testscripts/run_rdfa_validator_tests.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import glob
 import optparse
 import os
 import re
 import struct
 import subprocess
@@ skipping 355 matching lines @@
       tests = test_format.LoadTestFile(test_file)
       tests = [Test(options, test) for test in tests]
       if options.update:
         test_format.SaveTestFile(tests, test_file)
       processed += 1
   print '%s test files were processed.' % processed
 
 
 if __name__ == '__main__':
   main(sys.argv[1:])