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

src/trusted/validator_ragel/gen_dfa.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 collections
 import copy
 import itertools
 import optparse
 import re
 import StringIO
@@ skipping 1473 matching lines @@
 
   print '  one_instruction = '
   print '|\n'.join(printed_instrs)
 
   print '  ;'
   print '}%%'
 
 
 if __name__ == '__main__':
   main()