Add 1.9.3-p374

* http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-list/49138 (release mail in Japanese)
* http://svn.ruby-lang.org/repos/ruby/tags/v1_9_3_374/ChangeLog# Requesting a pull to sstephenson:master from sorah:193p374