Fix typo, that broke build on non-unix

Reviewed-by: Tim Hudson <tjh@openssl.org>

apps/rehash.c

diff --git a/apps/rehash.c b/apps/rehash.c
index 323fd15..b26cbf2 100644
--- a/apps/rehash.c
+++ b/apps/rehash.c
@@ -444,7 +444,7 @@
 
 int rehash_main(int argc, char **argv)
 {
-    BIO_print(bio_err, "Not available; use c_rehash script\n");
+    BIO_printf(bio_err, "Not available; use c_rehash script\n");
     return (1);
 }