Ruby » Ruby master

merge revision(s) 37169: [Backport #7169]

    use tty(1) to check if /dev/tty is usable or not

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@37204 b2dd03c8-39d4-4d8f-98ff-823fe69b080e