Added EmailRelay new package version 1.5 

As requested by Etienne Champetier <champetier.etienne@gmail.com>, please see (https://lists.openwrt.org/pipermail/openwrt-devel/2014-July/026632.html)

From: Federico Di Marco <fededim at gmail.com>

Body of explanation:
A new package has been added in packages feed under net/emailrelay directory, porting a simple SMTP proxy and store-and-forward message transfer agent (MTA) called EmailRelay (please see
http://emailrelay.sourceforge.net/) to OpenWRT.

The patch consists of the following files:
- Makefile: standard makefile of OpenWRT packages which downloads from sourceforge the source code and compiles it into a package using the uClibc++.
- Makefile.libstdc++: alternative makefile to perform compilation with the standard c++ library.
- files/emailrelay.auth: configuration file for emailrelay
- files/emailrelay.init: simple shell script for managing service installation and startup.

Sign-off:
Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or

(b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or

(c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it.

(d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved.

Signed-off-by: Federico Di Marco <fededim at gmail.com>

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