RT3984: Fix clang compiler warning on Mac OS X where %ld is used for uint64_t.

clang suggests %llu instead, but it isn't clear that is portable on
all platforms.

C99 and above define a handy macro for us, so we try to use that
definition and fall back to current definition if needed (though we
switch to 'u' for unsigned).

Reviewed-by: Matt Caswell <matt@openssl.org>

apps/enc.c

diff --git a/apps/enc.c b/apps/enc.c
index 628142a..18fcb95 100644
--- a/apps/enc.c
+++ b/apps/enc.c
@@ -567,8 +567,8 @@
 
     ret = 0;
     if (verbose) {
-        BIO_printf(bio_err, "bytes read   :%8ld\n", BIO_number_read(in));
-        BIO_printf(bio_err, "bytes written:%8ld\n", BIO_number_written(out));
+        BIO_printf(bio_err, "bytes read   :%8"PRIu64"\n", BIO_number_read(in));
+        BIO_printf(bio_err, "bytes written:%8"PRIu64"\n", BIO_number_written(out));
     }
  end:
     ERR_print_errors(bio_err);

apps/s_client.c

diff --git a/apps/s_client.c b/apps/s_client.c
index 2b69355..819cff3 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -2092,7 +2092,7 @@
         ssl_print_tmp_key(bio, s);
 
         BIO_printf(bio,
-                   "---\nSSL handshake has read %ld bytes and written %ld bytes\n",
+                   "---\nSSL handshake has read %"PRIu64" bytes and written %"PRIu64" bytes\n",
                    BIO_number_read(SSL_get_rbio(s)),
                    BIO_number_written(SSL_get_wbio(s)));
     }