Add package for chicken scheme compiler

This adds the chicken scheme compiler (4.11.0). Compiling this one takes quite a while.

Tested sucessfully on Samsung Chromebook 3 (XE500C13-K01US).

packages/chicken.rb

+require 'package'
+
+class Chicken < Package
+  version '4.11.0'
+  source_url 'https://code.call-cc.org/releases/4.11.0/chicken-4.11.0.tar.gz'
+  source_sha1 'b8b1e8b741a5ea5b318c449c3bf8a42f8de8ba69'
+
+  def self.build
+    system "make", "PLATFORM=linux"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install", "PLATFORM=linux"
+  end
+end