Ruby 1.9: force use syck yaml library (#8847, #4050).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@6462 e93f8b46-1217-0410-a6f0-8f06a7374b81

config/boot.rb

@@ -1,6 +1,11 @@
 # Don't change this file!
 # Configure your app in config/environment.rb and config/environments/*.rb
 
+if RUBY_VERSION >= '1.9'
+  require 'yaml'
+  YAML::ENGINE.yamler = 'syck'
+end
+
 RAILS_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(RAILS_ROOT)
 
 module Rails