SMTP proxy for SQLgrey whitelisting

This page describes the SMTP proxy that I started out with when I added sender whitelisting to SQLgrey. It's based on smtpprox. Below are two files: a modified version of smtpprox 1.2, and the patch itself. I later started using a combined SMTP proxy that also does DKIM sgning. I'm providing this in case someone only wants automatic sender whitelisting.