Add pwgen (2.07) package

The pwgen program generates passwords which are designed to be easily
memorized by humans, while being as secure as possible. The pwgen
program is designed to be used both interactively, and in shell scripts.

Tested as working properly on Samsung XE50013-K01US.

packages/pwgen.rb

+require 'package'
+
+class Pwgen < Package
+  version '2.07'
+  source_url 'https://pilotfiber.dl.sourceforge.net/project/pwgen/pwgen/2.07/pwgen-2.07.tar.gz'
+  source_sha1 '51180f9cd5530d79eea18b2443780dec4ec5ea43'
+
+  def self.build
+    system "./configure --prefix=/usr/local"
+    system "make"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install" 
+  end
+end