fix MITKRB5-SA-2005-002 KDC double-free and heap overflow

fix MITKRB5-SA-2005-002 KDC double-free and heap overflow

Fix for MITKRB5-SA-2005-002

* KDC double-free [CAN-2005-1174, VU#259798]
* krb5_unparse_name heap overflow [CAN-2005-1175, VU#885830]

Thanks to Daniel Wachdorf.

ticket: new
flags: pullup
target_version: 1.4.2

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@17298 dc483132-0cff-0310-8789-dd5450dbe970