Fix compile bugs in examples with hardcoded I/O callbacks

These were found by `all.sh test_baremetal`, so no need for a new test.
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 6d81626..3fa2b15 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -654,9 +654,6 @@
         first_try = 1; /* Next call will be a new operation */
     return( ret );
 }
-#endif /* MBEDTLS_SSL_CONF_RECV &&
-          MBEDTLS_SSL_CONF_SEND &&
-          MBEDTLS_SSL_CONF_RECV_TIMEOUT */
 
 typedef struct
 {
@@ -790,6 +787,9 @@
 
     return( mbedtls_net_send( io_ctx->net, buf, len ) );
 }
+#endif /* !MBEDTLS_SSL_CONF_RECV &&
+          !MBEDTLS_SSL_CONF_SEND &&
+          !MBEDTLS_SSL_CONF_RECV_TIMEOUT */
 
 #if defined(SNI_OPTION) || !defined(MBEDTLS_SSL_CONF_AUTHMODE)
 /*
@@ -1509,7 +1509,11 @@
 {
     int ret = 0, len, written, frags, exchanges_left;
     int version_suites[4][2];
+#if !defined(MBEDTLS_SSL_CONF_RECV) && \
+    !defined(MBEDTLS_SSL_CONF_SEND) && \
+    !defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT)
     io_ctx_t io_ctx;
+#endif
     unsigned char* buf = 0;
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
     unsigned char psk[MBEDTLS_PSK_MAX_LEN];