Switch to using Python 2.6

Simply updating the include in britney-py.c, rebuilding and changing
the shebang of britney.py appears to be enough to make the switch in my
tests, so we just do that for now at least.

Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>

britney.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python2.5 -u
+#!/usr/bin/python2.6 -u
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2001-2008 Anthony Towns <ajt@debian.org>

lib/britney-py.c

@@ -1,4 +1,4 @@
-#include <python2.5/Python.h>
+#include <python2.6/Python.h>
 
 #include "dpkg.h"