Re-order the base classes to prevent a crash in Linux.

In the initialization list of IOHandlerConfirm, *this is basically casting
IOHandlerConfirm to its base IOHandlerDelegate and passing it to constructor of
IOHandlerEditline which uses it and crashes as constructor of IOHandlerDelegate
is still not called. Re-ordering the base classes makes sure that constructor of
IOHandlerDelegate runs first.

It would be good to have a test case for this case too.

llvm-svn: 222816