asn1tostruct.py: use '#\!/usr/bin/env python', not '#\!/usr/bin/python'

Change-Id: I0686467e59b35e68bccb38ccfe645f5ccac97941
diff --git a/asn1/utils/asn1tostruct.py b/asn1/utils/asn1tostruct.py
index 3519407..1a2d95f 100755
--- a/asn1/utils/asn1tostruct.py
+++ b/asn1/utils/asn1tostruct.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 import re, os, sys, string
 import datetime