Display non working days on gantt according to settings (#2161).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@10750 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/helpers/gantt.rb

@@ -21,6 +21,7 @@ module Redmine
     class Gantt
       include ERB::Util
       include Redmine::I18n
+      include Redmine::Utils::DateCalculation
 
       # :nodoc:
       # Some utility methods for the PDF export