pull up r20109 from trunk

pull up r20109 from trunk

 r20109@cathode-dark-space:  raeburn | 2007-10-09 00:03:59 -0400
 ticket: 5777

 kt_file.c: Support multiple iterators active simultaneously, using a
 counter.  In get_entry, if the file was already open, rewind it to
 just after the version number, and don't close it when done.  Don't
 allow add or remove calls if any iterator is active.

 t_keytab.c: Test mixing two iterators with get_entry calls.

ticket: 5777

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-6@20170 dc483132-0cff-0310-8789-dd5450dbe970