Fix loading of util/debian.rb for custom facts

requirering the facter/util/debian.rb module causes
puppet warnings on wheezy hosts, and custom facts like
`$::debian_codename` cannot be evaluated.

    warning: Could not load fact file
      /srv/dev/projects/puppet/shared-modules//apt/lib/facter/debian_nextcodename.rb:
      no such file to load -- facter/util/debian

Removing the require line solves this.

lib/facter/debian_codename.rb

@@ -1,5 +1,7 @@
 begin
   require 'facter/util/debian'
+rescue LoadError
+  require "#{File.dirname(__FILE__)}/util/debian"
 end
 
 def version_to_codename(version)

lib/facter/debian_lts.rb

@@ -1,5 +1,7 @@
 begin
   require 'facter/util/debian'
+rescue LoadError
+  require "#{File.dirname(__FILE__)}/util/debian"
 end
 
 Facter.add(:debian_lts) do

lib/facter/debian_nextcodename.rb

@@ -1,5 +1,7 @@
 begin
   require 'facter/util/debian'
+rescue LoadError
+  require "#{File.dirname(__FILE__)}/util/debian"
 end
 
 def debian_codename_to_next(codename)

lib/facter/debian_release.rb

@@ -1,5 +1,7 @@
 begin
   require 'facter/util/debian'
+rescue LoadError
+  require "#{File.dirname(__FILE__)}/util/debian"
 end
 
 def debian_codename_to_release(codename)

lib/facter/ubuntu_nextcodename.rb

@@ -1,5 +1,7 @@
 begin
   require 'facter/util/ubuntu'
+rescue LoadError
+  require "#{File.dirname(__FILE__)}/util/debian"
 end
 
 def ubuntu_codename_to_next(codename)