Warning fixes from Christos Zoulas

- shadowed variables
- signed/unsigned confusion
- const lossage
- incomplete structure initializations
- unused code

lib/krb5/digest.c

@@ -727,8 +727,10 @@ krb5_digest_request(krb5_context context,
 	ireq.u.digestRequest.type = digest->init.type;
     }
 
-    if (ireq.u.digestRequest.digest == NULL)
-	ireq.u.digestRequest.digest = "md5";
+    if (ireq.u.digestRequest.digest == NULL) {
+	static char md5[] = "md5";
+	ireq.u.digestRequest.digest = md5;
+    }
 
     ret = digest_request(context, realm, ccache,
 			 KRB5_KU_DIGEST_ENCRYPT, &ireq, &irep);