Ruby

io.c: wipe away ioctl buffer

• io.c (setup_narg): wipe away expanded part of buffer to get rid
  of revealing uncleaned data. reported by Dongkwan Kim .

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49768 b2dd03c8-39d4-4d8f-98ff-823fe69b080e