Add vpnc package

packages/vpnc.rb

+require 'package'
+
+class Vpnc < Package
+  description 'client for cisco vpn concentrator'
+  homepage 'https://www.unix-ag.uni-kl.de/~massar/vpnc/'
+  version '0.5.3'
+  source_url 'https://www.unix-ag.uni-kl.de/~massar/vpnc/vpnc-0.5.3.tar.gz'
+  source_sha256 '46cea3bd02f207c62c7c6f2f22133382602baeda1dc320747809e94881414884'
+
+  depends_on 'libgcrypt'
+  depends_on 'openssl'
+  depends_on 'perl'
+
+  def self.build
+    system 'sed -i "s,\./makeman.pl,perl makeman.pl," Makefile'
+    system 'make'
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end