Adapt sources to configurable config.h name
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 44f04a4..48d5d30 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -23,7 +23,11 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_SSL_SERVER_NAME_INDICATION) && defined(POLARSSL_FS_IO)
 #define POLARSSL_SNI