pull up r19627 from trunk

pull up r19627 from trunk

 r19627@cathode-dark-space:  jaltman | 2007-06-22 14:58:09 -0400
 ticket: 5584

 Don't assume that WM_DESTROY is the last message to be received by a
 window.  Since the child windows are still alive and kicking by the
 time the parent receives WM_DESTROY, it's still possible to receive
 other messages after WM_DESTROY.

 If we free any window specific data when handling WM_DESTROY, we
 should reset the window data field as well, and check if we have a
 valid pointer when retrieving the window data field later.

ticket: 5584

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-6@19785 dc483132-0cff-0310-8789-dd5450dbe970