string.c: enable rdoc
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56913 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: enable rdoc
rb_str_downcase to enable rdoc.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56913 b2dd03c8-39d4-4d8f-98ff-823fe69b080e