Introduce versioning in the config files

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 5212fb3..af2c438 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -24,6 +24,8 @@
  *  limitations under the License.
  */
 
+#define MBEDTLS_CONFIG_VERSION 1
+
 /**
  * \name SECTION: System support
  *