avoid uninit variable and unreachable code warnings

most of these warnings are not problems because of ample
use of abort() calls.  However, the large number of warnings
makes it difficult to identify real problems.  Initialize
the variables to shut up the compilers.

Change-Id: I8477c11b17c7b6a7d9074c721fdd2d7303b186a8

lib/krb5/digest.c

@@ -244,7 +244,7 @@ digest_request(krb5_context context,
     DigestREP rep;
     krb5_error_code ret;
     krb5_data data, data2;
-    size_t size;
+    size_t size = 0;
     krb5_crypto crypto = NULL;
     krb5_auth_context ac = NULL;
     krb5_principal principal = NULL;