Merged r11542 from trunk to 2.3-stable.

use %r{} instead of // at lib/redmine/unified_diff.rb.

Syntax highlight is broken in gedit 2.28.4 on CentOS 6.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.3-stable@11548 e93f8b46-1217-0410-a6f0-8f06a7374b81