krb5: Update to 12.2.2.

Fixes security vulnerabilities CVE-2014-4341, CVE-2014-4342,
CVE-2014-4343, CVE-2014-4344 and CVE-2014-4345.
Merge pull request #4123 from falsifian/krb5

krb5: Update to 12.2.2.  (Please test before merging.)