io.c: [DOC] add missing $
$
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57977 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io.c: [DOC] add missing
$
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57977 b2dd03c8-39d4-4d8f-98ff-823fe69b080e