Merged r11399 from trunk to 2.2-stable (#13138)

not use htmlentities gem in rfpdf plugin.

Contributed by Jun NAITOH.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.2-stable@11400 e93f8b46-1217-0410-a6f0-8f06a7374b81