[krbdev.mit.edu #7179] krb5_cc_get_full_name() does not document how to free fullname_out

[Greg Hudson via RT]

It's not really a bug for klist (not kinit) to use free() for that, since 
it should be built in the same way as libkrb5.  But it doesn't set a very 
good example, so I'll fix it.