SCsub: Add python shebang as a hint for syntax highlighting

Also switch existing shebangs to "better" /usr/bin/env python.

(cherry picked from commit fc8ccd5b8c)

doc/tools/makerst.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
 import codecs