Use uint8_t for hash_file buffer.

ChangeLog

 2016-08-16  Niels Möller  <nisse@lysator.liu.se>
 
+	* examples/io.c (hash_file): Use uint8_t for buffer.
+
 	* sexp.c (sexp_iterator_check_type, sexp_iterator_check_types)
 	(sexp_iterator_assoc): Use const char * for caller's expression
 	types. Updated all callers.

examples/io.c

@@ -189,7 +189,7 @@ hash_file(const struct nettle_hash *hash, void *ctx, FILE *f)
 {
   for (;;)
     {
-      char buffer[BUFSIZE];
+      uint8_t buffer[BUFSIZE];
       size_t res = fread(buffer, 1, sizeof(buffer), f);
       if (ferror(f))
 	return 0;