Subject: add missing interpreter to etc/upgrade/sanity-check-stylesheets.pl

We install these scripts executable, so they need to have a valid
interpreter.

Bug: http://issues.bestpractical.com/Ticket/Display.html?id=18856

--- a/etc/upgrade/sanity-check-stylesheets.pl	2011-11-10 22:39:43.000000000 +0000
+++ b/etc/upgrade/sanity-check-stylesheets.pl	2011-11-10 22:40:24.000000000 +0000
@@ -1,3 +1,4 @@
+#!/usr/bin/env perl
 # BEGIN BPS TAGGED BLOCK {{{
 #
 # COPYRIGHT:
