mda-lmtp: Add a very basic MDA that uses LMTP to do the mail delivery.

mda-lmtp is a very basic MDA that uses LMTP to do the mail delivery.

It takes command line arguments similar to maildrop or procmail, reads an
email via standard input, and sends it over the given LMTP server.
Supports connecting to LMTP servers over UNIX sockets and TCP.

Since chasquid does not support direct LMTP local delivery, this can be
used as a workaround instead.

Example of use:
$ mda-lmtp --addr localhost:1234 -f juan@casa -d jose < email

cmd/mda-lmtp/test.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+set -e
+. $(dirname ${0})/../../test/util/lib.sh
+
+init
+
+# Build the binary once, so we can use it and launch it in chamuyero scripts.
+# Otherwise, we not only spend time rebuilding it over and over, but also "go
+# run" masks the exit code, which is something we care about.
+go build
+
+for i in *.cmy; do
+	if ! chamuyero $i > $i.log 2>&1 ; then
+		echo "# Test $i failed, log follows"
+		cat $i.log
+		exit 1
+	fi
+done
+
+success