Ruby2.0: remove "warning: class variable access from toplevel" in lib/plugins/rfpdf/lib/tcpdf.rb. Contributed by Jun NAITOH. git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.3-stable@11533 e93f8b46-1217-0410-a6f0-8f06a7374b81