use memset_s

lib roken includes support for memset_s() but it was not applied
to the Heimdal source tree.

Change-Id: I8362ec97a9be50205bb2d398e65b629b88ce1acd

kuser/kinit.c

@@ -677,7 +677,7 @@ get_new_tickets(krb5_context context,
     if (ntlm_domain && passwd[0])
 	heim_ntlm_nt_key(passwd, &ntlmkey);
 #endif
-    memset(passwd, 0, sizeof(passwd));
+    memset_s(passwd, sizeof(passwd), 0, sizeof(passwd));
 
     switch(ret){
     case 0: