ECDH alternative implementation support

Add alternative implementation support for ECDH at the higher layer
diff --git a/library/version_features.c b/library/version_features.c
index 9f97c7b..7b08f04 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -93,6 +93,9 @@
 #if defined(MBEDTLS_DES_ALT)
     "MBEDTLS_DES_ALT",
 #endif /* MBEDTLS_DES_ALT */
+#if defined(MBEDTLS_ECDH_ALT)
+    "MBEDTLS_ECDH_ALT",
+#endif /* MBEDTLS_ECDH_ALT */
 #if defined(MBEDTLS_XTEA_ALT)
     "MBEDTLS_XTEA_ALT",
 #endif /* MBEDTLS_XTEA_ALT */