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

tools/run_test_via_ssh_test.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 subprocess
 import unittest
 
 import run_test_via_ssh
 
 
 class Test(unittest.TestCase):
 
   def test_escaping(self):
     # All ASCII characters.
     for ascii_value in range(1, 256):
       # Make sure to put a character after: $ behaves well when on its own,
       # but not so well when followed by something else.
       c = '--%s--' % chr(ascii_value)
       escaped = run_test_via_ssh.ShellEscape(c)
       result = subprocess.check_output('echo ' + escaped, shell=True)
       self.assertEquals(result, '%s\n' % c)
 
 
 if __name__ == '__main__':
   unittest.main()