Ruby

win32.c: fix dup2 return value

• win32/win32.c (rb_w32_dup2): should return the new fd on
  success, while msvcrt returns 0 wrongly.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51841 b2dd03c8-39d4-4d8f-98ff-823fe69b080e