prevent unintended sign extension errors

When an unsigned char is shifted << 24 bits its type will be
promoted to signed 32-bits.   If the value is then assigned to
an unsigned 64-bit value sign extension will occur.

Prevent the unwanted sign extension by explicitly casting the
value to unsigned long before shifting.

Change-Id: Iabeac0f17dc3229a2dc89abe71960a8ffbf523f8

lib/gssapi/mech/gss_krb5.c

@@ -572,7 +572,7 @@ gsskrb5_extract_authtime_from_sec_context(OM_uint32 *minor_status,
 
     {
 	unsigned char *buf = data_set->elements[0].value;
-	*authtime = (buf[3] <<24) | (buf[2] << 16) |
+	*authtime = ((unsigned long)buf[3] <<24) | (buf[2] << 16) |
 	    (buf[1] << 8) | (buf[0] << 0);
     }